Cruz has been diagnosed with autism, depression, and ADHD, and has a history of hostile behavior and aggression. The police had received 39 calls to his mother's house. Also, Cruz was reported to the FBI twice, once for a YouTube comment in September 2017, in which he said "I'm going to be a professional school shooter, though it fell through after the FBI was "unable to track him down."
The other on January 5, 2018, when a person close to Cruz "provided information about Cruz's gun ownership, desire to kill people, erratic behavior, and disturbing social media posts, as well as the potential of him conducting a school shooting."
Stoneman Douglas High School shooting
On February 14, 2018, he killed 17 people and wounded 14 people, sending students running into the streets in panic and terror. Though he was initially able to flee the scene by dropping his weapons and blending in with the terrified fleeing students, the police identified him through school surveillance footage. He was eventually stopped in Coral Springs Florida, about 79 minutes after the shooting initially began.
Cruz armed himself with an AR-15-style semi-automatic rifle with multiple loaded magazines. Upon entering the school, he pulled a fire alarm and began shooting at teachers and students. Upon his capture at 3:40 PM, he was sent to the hospital, but then ultimately sent to Broward County Jail.
The exact reasons behind Cruz's attack remain unknown, but there are many possible contributing factors. Nikolas Cruz suffered from mental illness exacerbated by violence and aggression. He was transferred to a special ed school in 2014 but ended up transferring to Marjory Stoneman Douglas High School in 2016. He got suspended on September 20, and only 8 days later attempted to kill himself by slitting his wrists and drinking gasoline. He also expressed plans to buy a gun, while getting into many fights and having dished out many threats.
The death of his mother on November 1, 2017, may have influenced him. Cruz watched his adoptive father die in 2004, so Cruz lived with relatives and younger brother after both of his parents had died. He posted a series of violent and possibly threatening pictures on his Instagram account. He also used his account to express his racist views and broadcast threats to others, including his school. He posted dozens of pictures showcasing his weapons, posted alongside his extremist views. Even after his January 5th case, the police failed to investigate the matter, breaking protocol and enabling the assault.
He is being charged with 17 counts of premeditated murder, which may warrant a death penalty conviction. After his arraignment, he was held in an isolated cell on suicide watch.
The State of Flordia plans for an execution for Cruz later in the year.