An armed officer who stood outside a Florida school as a gunman killed 17 people has been arrested and faces multiple charges, including child neglect and perjury.
Scot Peterson, a security guard at the Marjory Stoneman Douglas High School, did not enter as shots rang out last year and later resigned.
US President Donald Trump called him a "coward" for not acting.
Mr Peterson said he did not know where the gunfire was coming from.
Seventeen students were killed in the massacre in Parkland on Valentine's Day in 2018.
Nikolas Cruz, 19, a former student at the school, has been charged with 17 counts of premeditated murder. Police have said he admitted the shooting.
Soon afterwards, authorities released footage showing Mr Peterson waiting outside the school as the shooting was taking place.
Following an investigation by the Florida Department of Law Enforcement (FDLE), Mr Peterson was arrested on Tuesday on seven counts of neglect of a child, three counts of culpable negligence and one count of perjury.
The investigation showed Mr Peterson "did absolutely nothing" to prevent the shooting, FDLE Commissioner Rick Swearingen said in a statement.
"There can be no excuse for his complete inaction and no question that his inaction cost lives," he added.
Broward County Sheriff Scott Israel voiced his anger after viewing the footage of Mr Peterson remaining outside the building for four minutes while the killings were taking place. The shooting lasted just six minutes.
"I am devastated. Sick to my stomach. He never went in," Sheriff Israel said, adding that he should have entered and "killed the killer".
President Trump said the officer "certainly did a poor job" and branded him a coward.
Mr Peterson maintained he believed the shots were coming from outside the school.
He told NBC that he "didn't get it right", but added: "Those are my kids in there. I never would have sat there and let my kids get slaughtered."