On Saturday, New Hampshire’s attorney general, John Fomella, said Madore shot dead Bradley Haas, 63, before a police officer killed him.
All patients at the 185-bed hospital in the state capital of Concord were safe, but Mr Haas could not be saved despite attempts to resuscitate him.
“Investigators with the New Hampshire State Police have searched and cleared a suspicious box truck near the scene,” Mr Fomella added.
“They determined the truck poses no safety risk.”
Guard’s actions ‘saved many’
Madore used a 9mm pistol when he shot unarmed Mr Haas, whose actions “saved a lot of lives”, Mr Fomella said.
Police also found an AR-style rifle, a tactical vest and several ammunition supplies in a truck at the hospital car park.
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Mr Haas lived in Franklin, a small city about 20 miles (32 kilometres) from Concord, and he worked as a police officer for 28 years before rising to become police chief, according to Mr Fomella.
The Franklin Police Department said he dedicated decades to the city and police department before retiring in 2008.
Friday’s shooting was the latest act of violence at a hospital in the US, with medical centres across the country struggling to adapt to the growing threats.