As I understand it, the Security Guard (unarmed), and the athletic director, went to confront the armed attacker .
Both are among the deceased.
News Source: http://www.foxnews.com/us/2018/02/20/parkland-shooting-victims-include-young-students-coach-who-saved-others-in-florida-high-school.html
Aaron Feis
An assistant football coach and security guard, Aaron Feis used his own body to shield students as gunfire rang out
in the school, the Marjory Stoneman Douglas High School football team said on social media."
" When the initial calls about the shooting came through the school’s walkie-talkie, Feis, 37, responded to his duties as a security guard, according to the newspaper."
Chris Hixon
" Marjory Stoneman Douglas athletic director Chris Hixon was always willing to lend a helping hand, his colleagues, friends and neighbors say."
"Hixon, 49, was always there. And he was there, in his role on the school’s security force, when the gunman began to shoot.
A Naval Reservist, Hixon was deployed to Iraq in 2007, according to the Sun Sentinel."
Mr. Hixon was not a Broward County Sheriff’s Deputy working as a school resource officer.
Supposedly a Deputy Peterson was the SRO but aside from some hearsay about Peterson’s location it has not been confirmed exactly where Peterson was that day.
Initial comments had the SRO off campus and then in subsequent comments you could see a lot of equivocating from the Sheriff’s Department and the school district as to where the SRO was.
They were dancing the line of lying to the public while giving themselves some wiggle room to back out of it in case they got caught.