The gunman, named by police Colt Gray, was a student at Apalachee High School, in Barrow County, where the attack took place, leading to the school being placed on lockdown and officers swarming the location before he gave himself up.
The four victims who died have been named as students Mason Schermerhorn and Christian Angulo, both 14, and teachers Richard Aspenwall, 39, and Christina Irimie, 53.
Suspect previously interviewed
In May last year, the FBI received several anonymous tips about online threats to commit a school shooting, Chris Hosey, director at the Georgia Bureau of Investigation said.
The Jackson County Sheriff’s Office located a possible suspect, he said – the then 13-year-old Gray.
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They interviewed Gray and his father, who stated he had hunting guns but that his son didn’t have unsupervised access to them.
Gray himself denied making the threats online and at the time there was no probable cause for arrest and no further action was taken, Mr Hosey said.
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Now, authorities are re-investigating the incident and any possible connection it may have to the most recent shooting.
“We are also aware of some previous contacts that the Department of Family and Children Services had had with the suspect and his family, and we are pursuing that avenue as well,” Mr Hosey added.
Nine people, eight students and one teacher, were taken to hospital with injuries from the attack, but it was said that they are all expected to make a recovery.
Gray is being charged as an adult and the attack was carried out using an AR-style weapon – a gun often associated with school shootings.
While police are still chasing down a number of leads, and carrying out their investigations, they said that the actions of teachers saved a number of lives.
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Grandmother of student on Georgia shooting
Authorities were alerted to the attack due to a new alarm system that had only been implemented a week earlier.
Sheriff Jud Smith said: “All of our teachers are armed with a form of ID, this alarms us and alerts law enforcement officers after buttons are pressed on the ID.
“It alerts us there is an active situation at the school. We’ve had that about a week now.”
‘Just so you know, I love you’
The words “hard lockdown” appeared on a screen in Layla Ferrell’s health class as lights began flashing.
She and her terrified classmates piled desks and chairs in front of the door to create a barrier, she said.
Meanwhile, Kaylee Abner was in her geometry class when she heard gunshots.
Along with her classmates she hid behind their teacher’s desk, before they began flipping the desk to try and barricade the classroom door, she said.
Donald Trump says a meeting is being set up between himself and Vladimir Putin – and that he and Barack Obama “probably” like each other.
Republican US president-elect Mr Trump spoke to reporters at his Mar-a-Lago resort in Florida on Thursday, saying Russian president Mr Putin “wants to meet, and we are setting it up”.
“He has said that even publicly and we have to get that war over with. That’s a bloody mess,” Mr Trump said.
Kremlin spokesperson Dmitry Peskov said on Friday there was a “mutual desire” to set up a meeting – but added no details had been confirmed yet and that there may be progress once Mr Trump is inaugurated on 20 January.
“Moscow has repeatedly declared its openness to contacts with international leaders, including the US president, including Donald Trump,” Mr Peskov added.
“What is required is a mutual desire and political will to conduct dialogue and resolve existing problems through dialogue. We see that Mr Trump also declares his readiness to resolve problems through dialogue. We welcome this. There are still no specifics, we proceed from the mutual readiness for the meeting.”
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Trump on Obama: ‘We just got along’
Mr Trump also made some lighter remarks regarding a viral exchange between himself and former Democrat President Barack Obamaat Jimmy Carter’s funeral on Thursday.
The pairsat together for the late president’s service in Washington DC on Thursday, and could be seen speaking for several minutes as the remaining mourners filed in before it began.
Mr Obama was seen nodding as his successor spoke before breaking into a grin.
Asked about the exchange, Mr Trump said: “I didn’t realise how friendly it looked.
“I said, ‘boy, they look like two people that like each other’. And we probably do.
“We have a little different philosophies, right? But we probably do. I don’t know. We just got along. But I got along with just about everybody.”
The amicable exchange comes after years of criticising each other in the public eye; it was Mr Trump who spread the so-called “birther” conspiracy theory about Mr Obama in 2011, falsely asserting that he was not born in the United States.
Mr Trump has repeatedly attacked the Obamas, saying the former president was “ineffective” and “terrible” and calling former first lady Michelle Obama “nasty” as recently as October last year.
On Kamala Harris’s campaign trail last year, Mr Obama said Mr Trump was a “78-year-old billionaire who has not stopped whining about his problems since he rode down his golden escalator nine years ago”, while the former first lady said that “the consequences of him ever being president again are brutally serious.”
The US Supreme Court has rejected a last-ditch attempt by Donald Trump to delay sentencing in the Stormy Daniels hush money case.
The president-elect was convicted on 34 counts last May in New York of falsifying business records relating to payments made to Ms Daniels before the 2016 presidential election.
Prosecutors claimed he had paid her $130,000 (£105,300) in hush money to not reveal details of what Ms Daniels said was a sexual relationship in 2006.
Mr Trump has denied any liaison with Ms Daniels or any wrongdoing.
By a majority, the Supreme Court found his sentencing would not be an insurmountable burden during the presidential transition since the presiding judge, Juan M Merchan, has indicated he will not give Mr Trump jail time, fines or probation.
Mr Trump’s attorneys argued that evidence used in the Manhattan trial violated last summer’s Supreme Court ruling giving Mr Trump broad immunity from prosecution over acts he took as president.
At the least, they said, the sentencing should be delayed while their appeals play out to avoid distracting Mr Trump during the presidential transition.
Mr Trump’s attorneys went to the justices after New York courts refused to postpone sentencing.
Judges in New York found that the convictions related to personal matters rather than Mr Trump’s official acts as president.
Mr Trump’s attorneys called the case politically motivated, and they said sentencing him now would be a “grave injustice” that threatens to disrupt the presidential transition as the Republican prepares to return to the White House.
Mr Trump has said he will appeal again: “I respect the court’s opinion – I think it was actually a very good opinion for us because you saw what they said, but they invited the appeal and the appeal is on the bigger issue. So, we’ll see how it works out,” he said at a dinner with Republican governors at his private club in Florida.
Because the New York case was a state, rather than federal crime, Mr Trump will not be able to pardon himself when he takes office on 20 January.