At 1:37 p.m., hours before the shooting started, Vargas called 9-1-1 and reported he was being followed, asking the dispatcher to run the license plate of a vehicle parked outside his apartment.

[1][7][8][9] He proceeded to go to his balcony on the fourth floor of the building and fired 10 to 20 bullets into the street, fatally hitting 33-year-old Carlos Gavilanes as he got out of his car.

[7][8][9] Vargas then kicked open the door of apartment 304, where he shot and killed the residents, 64-year-old Patricio Simono, his 51-year-old wife Merly Niebels, and their 17-year-old daughter Priscilla Perez.

After negotiations reportedly broke down, authorities decided to send in a six-officer SWAT team to rescue the hostages.

[5][18] According to several LA Fitness customers, Vargas frequented the local gym and often lifted weights as a way to channel out pent-up anger.

[4][13] He worked at the media services department at Miami Dade College's North Campus starting in 2004,[19] and although his initial performance evaluations judged him positively, they began noting a lack of social skills.

Vargas was eventually forced to resign in 2008 after the school found he downloaded inappropriate files, including a computer hacking tutorial from The Anarchist Cookbook.

Several months afterward, Miami Dade College received anonymous online threats that were traced to a public library in Hialeah, though Vargas was suspected of being the sender.

[14] Prior to the shooting, Vargas had been working as a graphic design artist for Bullet Line, a promotional company, from May to October 2012.