FORT LAUDERDALE, Fla. (AP) — As teachers returned Friday to a high school where a shooter killed 17 people, Florida's governor proposed banning the sale of firearms to anyone younger than 21.

Gov. Rick Scott announced the proposal as part of a plan to prevent gun violence.

He also called for a trained law enforcement officer for every 1,000 students at every school in Florida by the time the 2018 school year begins. Marjory Stoneman Douglas High School in Parkland had one armed resource officer, who never entered the school during the Feb. 14 shooting.

That failure, plus reports of a delay in security camera footage scanned by responding police and several records about the 19-year-old suspect's troubled background added to what the Florida House speaker called an "abject breakdown at all levels."

The Valentine's Day shooting has reignited national debate over gun laws and school safety, including proposals by President Donald Trump and others to designate more people — such as trained teachers — to carry arms on school grounds. Gun-control advocates, meanwhile, have redoubled calls for bans or further restrictions on assault rifles.

Teachers have begun returning to the school to collect belongings from classrooms that have been off-limits since the slayings. After an orientation Sunday for teachers and students, classes resume Wednesday.

"Our new normal has yet to be defined, but we want to get back to it," said geography teacher Ernest Rospierski, whose classroom is on the third floor of the three-story building attacked Feb. 14. Officials have said that building will be torn down.

History teacher Ivy Schamis was teaching a Holocaust class when the shooter fired into her classroom. She's planning to return Monday to collect items from the room, including a yellow banner that reads, "Never Again," referring to the Holocaust. She wants it hanging in her next classroom. "That's a Holocaust banner and now that's what our slogan is becoming after this tragedy."

The school resource officer took up a position viewing the western entrance of that building for more than four minutes after the shooting started on Feb. 14, but "he never went in," Broward County Sheriff Scott Israel said at a news conference. The shooting lasted about six minutes.

The officer, Scot Peterson, was suspended without pay and placed under investigation, then chose to resign, Israel said. When asked what Peterson should have done, Israel said the deputy should have "went in, addressed the killer, killed the killer."

The sheriff said he was "devastated, sick to my stomach. There are no words. I mean these families lost their children. We lost coaches. I've been to the funerals. ... I've been to the vigils. It's just, ah, there are no words."

Trump weighed in Friday, saying Peterson was either a "coward" or "didn't react properly under pressure."

A telephone message left at a listing for Peterson by The Associated Press wasn't returned. No one answered the door when an AP reporter later went to Peterson's home in West Palm Beach suburb.

Meanwhile, officials said a communication issue arose between the person reviewing the school's security system footage and officers who responded to the school.

Coral Springs Police Chief Tony Pustizzi said Thursday that the footage being reviewed was 20 minutes old, so the responding officers were hearing that the shooter was in a certain place while officers already there were saying that wasn't the case. Pustizzi said the confusion didn't put anyone in danger.

Shooting suspect Nikolas Cruz, 19, has been jailed on 17 counts of murder and has admitted the attack, authorities have said. Cruz owned a collection of weapons. Defense attorneys, state records and people who knew him have described troubling incidents going back years.

Broward County incident reports show that unidentified callers contacted authorities with concerns about Cruz in February 2016 and November 2017. The first caller claimed to have third-hand information that Cruz planned to shoot up the school. The information was forwarded to the Stoneman Douglas resource officer. The second caller said Cruz was collecting guns and knives and believed "he could be a school shooter in the making."

Also in November 2017, Cruz got in a fight with the adult son of a woman he was staying with shortly after his mother died, according to a Palm Beach County Sheriff's Office report. On Nov. 28, a 22-year-old man at the Lake Worth home told the responding deputy the he tried to calm down Cruz, who had been punching holes in walls and breaking objects, but Cruz hit him in the jaw, and the man hit Cruz back.

A short time later at a nearby park, Cruz told the deputy he had been angry because he misplaced a photo of his recently deceased mother, and he apologized for losing his temper.

The other man told the deputy he wanted Cruz to calm down before coming home, but didn't want him arrested.

Politicians under pressure to tighten gun laws in response to the slayings floated plans, but most fell short of reforms demanded by student activists who converged Wednesday on Florida's Capitol.

The governor's proposal would ban bump stocks and require mandatory active shooter training at all schools. Students, teachers and staff must complete all training and "code red" drills by the end of the first week of each semester.

Scott called for keeping guns away from violent and mentally ill people and providing more funds for mental health programs. His proposal would create a "violent threat restraining order," allowing a court to prohibit a violent or mentally ill person from purchasing or possessing a firearm or any other weapon, based on sworn evidence. It would also strengthen gun purchase and possession restrictions for mentally ill people.

Florida House Speaker Richard Corcoran said Thursday that his chamber will recommend creating a special commission to investigate the "abject breakdown at all levels" that led to the shooting deaths.

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