US President Donald Trump has cast doubt on the character of an armed deputy who failed to intervene during last week's school shooting in Florida, saying he froze or was a "coward".
"They're trained, they didn't react properly under pressure or they were a coward," he said, calling out the school resource officer Scot Peterson by name.
The attack saw 17 people lose their lives, one of the deadliest mass shootings at a public school in US history.
"When it came time to get in there and do something, he didn't have the courage or something happened," Mr Trump said. "But he certainly did a poor job. There's no question about that."
Trump suggests officer at Florida school was a 'coward' | https://t.co/W7rGAnymFj pic.twitter.com/t9ypzfqWs9
— RTÉ News (@rtenews) February 23, 2018
Mr Peterson resigned after being suspended without pay, following an internal investigation showed he failed to enter the school to confront the gunman during the attack.
"He was on duty and in uniform as the resource officer posted at Marjory Stoneman Douglas High School ... was the only law enforcement officer present last week when the attack started," Broward County Sheriff Scott Israel said.
Mr Peterson's actions were caught on video during the massacre, which was carried out by a lone gunman wielding a semi-automatic AR-15-style assault rifle.
Nikolas Cruz, a 19-year-old former student, was later arrested and charged with 17 counts of premeditated murder.

"What I saw was a deputy arrive at the west side of Building 12, take up a position and he never went in," Sheriff Israel said, referring to the building on campus where authorities said the bulk of the shooting occurred.
He told reporters the shooting in the Fort Lauderdale suburb of Parkland lasted six minutes, and that Mr Peterson reached the building under attack about 90 seconds after the first shots were fired, then lingered outside for at least four minutes.
Asked what the deputy should have done, Sheriff Israel replied: "Went in. Addressed the killer. Killed the killer."
"He never went in": An armed deputy who "failed to confront" the Florida gunman has resigned pic.twitter.com/BFmYHHJbta
— RTÉ News (@rtenews) February 23, 2018
Mr Peterson has not given a reason for why he did not enter the building, Sheriff Israel said. Neither the deputy nor any representatives could immediately be reached for comment.
Sheriff Israel said he had decided on the basis of his review of the video to suspend Mr Peterson, but the deputy resigned first.
The sheriff said two other deputies have been placed on restricted duty pending an internal investigation into whether they properly handled two telephone tips, received in 2016 and 2017, warning that Cruz might be inclined to commit a school shooting.
Authorities have said that Cruz, who was expelled from Stoneman Douglas High last year for unspecified disciplinary problems, made his getaway moments after the shooting by blending in with students fleeing the school for safety.
Mr Trump has indicated he is weighing calls for a toughening of gun regulations in the wake of the Parkland shooting, but has also responded with a deeply controversial call to arm teachers.
Read more:
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Florida governor calls for police officer in every public school
The Republican governor of Florida has called for a police officer to be assigned to every public school in the state, and for the minimum age for gun purchases to be raised from 18 to 21.
"I'm calling for a mandatory law enforcement officer in every public school," Rick Scott told a news conference, as he unveiled a raft of safety measures in the wake of last week's shooting.
Mr Scott said the southern US state "will require all individuals purchasing firearms to be 21 or older," and intended to make it "virtually impossible" for anyone with "mental issues" to acquire a weapon.
The shooting has renewed a national debate between proponents of gun rights, as enshrined in the Second Amendment to the US Constitution, and advocates for tougher restrictions on firearms.
High school students from Stoneman Douglas and elsewhere around the country have launched a protest and lobbying campaign demanding new curbs on assault weapons.
The US Congress has long been deadlocked on the gun debate, accomplishing nothing despite a spate of mass shootings and polls suggesting that Americans support stricter gun laws by a two-to-one margin.