In an instant, a large section of the Francis Scott Key Bridge was gone – as dozens of its steel beams collapsed into the water after being hit by a cargo ship.
Emergency services are still at the scene and details about casualties are still emerging.
Sky News has spoken to a number of maritime and engineering experts to try and understand what might have happened – and what issues may have been at play.
Was human error to blame?
Professor Helen Sampson, an expert at the Seafarers International Research Centre at Cardiff University, says the crash may have been caused by someone’s mistake.
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She told Sky News: “Was there some sort of miscommunication or misunderstanding between the pilot and the crew? Or was there a pilot error?”
The time of day when the disaster occurred – around 1.30am local time – gives rise to concerns about tiredness, she added.
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“The time makes me also wonder whether there was an element of fatigue at play…
“It’s almost always the case that we focus on human error at the individual level, it’s almost always the case that there’s a broader context which has resulted in that human error, like fatigue and the demands made on pilots or on crews.”
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0:46
‘They thought it was an earthquake’
What about a mechanical problem?
However, another maritime safety expert says the “most likely” cause of the crash was a failure in the ship’s machinery.
David McFarlane, director of Maritime Risk and Safety Consultants Ltd, told Sky News: “The first thing that springs to my mind is: was there a sudden fault with the ship’s engines or the steering gear?”
Mr McFarlane said a human error was less likely because of the number of people who would have been on duty.
“There should be no room for one-person errors because one of the other people should jump in and say ‘hang on’,” he said.
“The most likely cause of this is a failure in machinery or steering gear, but we just won’t know until the authorities have been on board. And even then, they’re unlikely to say what’s been going on for some considerable time.”
Prof Sampson said a mechanical failure with the steering gear or something similar would be the “most dramatic” explanation for what happened.
Officials have confirmed the ship that crashed into the bridge had issued a mayday call and had lost power.
Was there a design flaw in the bridge?
Opened in 1977, the Francis Scott Key Bridge is named after the poet who wrote the words to the Star Spangled Banner, the American national anthem.
Constructed from steel, it was 1.6 miles long and not dissimilar to some bridges in the UK, one expert told Sky News.
Julian Carter, a structural and civil engineering expert, said these structures are simple in concept – but “very weak” at certain points.
“It’s what we call a continuous structure every little piece is connected to another – and unfortunately it’s a catastrophic collapse.”
Professor Barbara Rossi, an expert in engineering science at the University of Oxford, said the impacting force of the cargo ship must have been “immense” to lead to the collapse of the concrete structures underpinning the bridge.
“We should not speculate around if such huge impact forces should have been taken into account at the design stage,” she added.
There has also been discussion about whether “dolphins” (steel structures embedded in the seabed to stop or divert a ship) or artificial islands may have been inadequate.
Bridge designer Robert Benaim said: “I do not know what the arrangements were for this bridge but major bridges over shipping lanes must have substantial protection for piers or columns.”
He added: “If piers are not protected adequately then they are vulnerable to ship collision. Clearly the protection of the piers in this instance was inadequate. A pier or column of a bridge could never resist the impact of a large ship. They must be protected from collision.”
It was the first time a US president had been convicted of or charged with a criminal offence.
Trump had tried to cover up “hush money” payments to a porn star in the days before the 2016 election.
When Stormy Daniels‘ claimsof a sexual liaison threatened to upend his presidential campaign, Trump directed his lawyer to pay $130,000 (£102,000) to keep her quiet.
The payment buried the story and he later won the presidency.
Trump denied the charges and said the case was politically motivated. He also denied the sexual encounter took place.
New York State Supreme Court Justice Juan Merchan today delayed the sentencing, which had been due to take place on Tuesday.
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The office of district attorney Alvin Bragg had asked the judge to postpone all proceedings until Trump finishes his four-year presidency, which starts on 20 January.
Trump’s lawyers say the case should be dismissed because it will create “unconstitutional impediments” to his ability to govern.
Responding to Friday’s decision, a Trump campaign spokesman said: “The American People have issued a mandate to return him to office and dispose of all remnants of the Witch Hunt cases.”
The judge set a 2 December deadline for Trump’s lawyers to file their motion, while prosecutors have until 9 December to respond.
He did not set a new date for sentencing or indicate when he would rule on any motion to throw out the case.
Even before Trump’s win in this month’s election, experts said a jail term was unlikely and a fine or probation more probable.
But his resounding victory over Kamala Harris made the prospect of time behind bars or probation even less likely.
Trump, 78, was also charged last year in three other cases.
One involved him keeping classified documents after he left office and the other two centre on alleged efforts to overturn his 2020 election loss.
A Florida judge dismissed the documents case in July, the Georgia election case is in limbo, and the Justice Department is expected to wind down the federal election case as it has a policy of not prosecuting a sitting president.
Trump last week nominated his lawyers in the hush money case, Todd Blanche and Emil Bove, for senior roles in the Justice department.
When he re-enters the White House, Trump will also have the power to shut down the Georgia and New York cases.
Donald Trump has pledged for years to surround himself with ultra-loyalists who can mould his government to his vision without barriers.
That’s precisely why he picked Matt Gaetz. Now he’s out, Pam Bondi is in and she’s equally loyal.
Gaetz was uniquely unpopular on Capitol Hill but ultra-MAGA and ultra-loyal to the president-elect.
He was chosen by the president-elect to do his bidding inside the Justice Department as attorney general.
Critics called his pick “a red alert moment for democracy” and the man a “gonzo agent of chaos” – language that would surely only affirm Trump’s decision in his own proudly disruptive mind.
If it wasn’t for the fact that the president-elect is himself a convicted felon, and a man found liable in a civil court of his own sexual offences, the prospect of Gaetz, with all his baggage, making it through the nomination process would have seemed remote.
But Donald Trump’s return to the White House suggested anything is possible.
And so, beyond his loyalty, Gaetz was Trump’s test for his foot soldiers on Capitol Hill. How loyal were they? Would they wave through anyone he appointed?
It turns out that Gaetz, and the storm around his private life, was too much for a proportion of them.
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At least five Senate Republicans were flatly against Matt Gaetz’s confirmation. We understand that they communicated to other senators and those close to Trump that they were unlikely to be swayed.
They included the Republican old guard like Senator Mitch McConnell.
Beyond the hard “no” senators, there were between 20 and 30 other Republicans who were very uncomfortable about having to vote for Gaetz on the Senate floor.
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2:23
Trump pick Matt Gaetz withdraws
The key question is whether Gaetz was Trump’s intentional wild card crazy choice that he knew, deep down, would probably never fly.
Was Gaetz the candidate he had accepted would be vetoed by senators – who would then feel compelled to wave the rest of his nominees through?
Will Pete Hegseth’s alleged sexual impropriety concern them as they consider the suitability of the former Fox News host and army major to run the Department of Defence?
What about Tulsi Gabbard, the candidate Russian state TV calls ‘our girl’, and the appropriateness of her running America’s intelligence agencies?
These are all appointments that the politicians on Capitol Hill must consider and confirm in the weeks ahead.
We don’t yet know who Trump will choose to direct the FBI.
There are some names being floated which will make the establishment of Washington shudder but then that’s precisely why Trump was elected. He is the disrupter. He said so at every rally, on repeat.
He was quick to pivot to another name to replace Gaetz.
Bondi is the former attorney general of Florida. Professionally she is in a different league to Gaetz. She’s been a tough prosecutor, with a no-nonsense reputation.
She is also among the most loyal of loyalists. Her attachment to Trump stretches way back.
I first came across her in Philadelphia in November 2020 when she was among Trump surrogates claiming the election back then had been stolen from them by Joe Bidenand the Democrats.
She was a key proponent of the false claims the election had been rigged and Trump was the rightful winner.
The court cases concluding that was all nonsense didn’t seem to convince her.
Now she is poised to head up the Department of Justice as the country’s top law enforcement official.
Within hours of taking office, president-elect Donald Trump plans to begin rolling out policies including large-scale deportations, according to his transition team.
Sky News partner network NBC News has spoken with more than half a dozen people familiar with the executive orders that his team plans to enact.
One campaign official said changes are expected at a pace that is “like nothing you’ve seen in history”, to signal a dramatic break from President Joe Biden’s administration.
Mr Trump is preparing on day one to overturn specific policies put in place by Mr Biden. Among the measures, reported by sources close to the transition team, are:
• The speedy and large-scale deportations of illegal immigrants
• Ending travel reimbursement for military members seeking abortion care
• Restricting transgender service members’ access to gender-affirming care
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But much of the first day is likely to focus on stopping illegal immigration – the centrepiece of Trump’s candidacy. He is expected to sign up to five executive orders aimed at dealing with that issue alone after he is sworn in on 20 January.
“There will without question be a lot of movement quickly, likely day one, on the immigration front,” a top Trump ally said.
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“There will be a push to make a huge early show and assert himself to show his campaign promises were not hollow.”
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2:23
Donald Trump ally Matt Gaetz has withdrawn his name from consideration to be the next US attorney general.
But Mr Trump’s campaign pledges also could be difficult to implement.
Deporting people on the scale he wants will be a logistical challenge that could take years. Questions also remain about promised tax cuts.
Meanwhile, his pledge to end the war between Russia and Ukraine in just 24 hours would be near impossible.
Even so, advisers based at Mr Trump’s Mar-a-Lago resort or at nearby offices in West Palm Beach, Florida, are reportedly strategising about ending the wars in Ukraine and the Middle East.
Following his decisive victory on 5 November, the president-elect has moved swiftly to build a cabinet and senior White House team.
As of Thursday, he had selected more than 30 people for senior positions in his administration, compared with just three at a similar point in his 2016 transition.
Stephen Moore, a senior economic adviser in Mr Trump’s campaign, told NBC News: “The thing to realise is Trump is no dummy.
“He knows he’s got two to three years at most to get anything done. And then he becomes a lame duck and we start talking about [the presidential election in] 2028.”