He held jobs as a security guard and appeared to have a fondness for law enforcement, having once talked to friends about becoming a police officer.
He had twice come under investigation by the FBI — once for comments suggesting an affinity for Islamist groups, and a second time for vague connections to another Florida man who traveled to Syria to become a suicide bomber.
Neither probe turned up evidence of wrongdoing, and Mateen had a blemish-free record when he applied for a Florida license to carry concealed weapons and again when he legally purchased two firearms, including an assault-style semiautomatic rifle, just a few days before the shootings.
The older Mateen would eventually open a business and attempt to dabble in Afghan politics from afar, starting a You Tube channel in Florida in which he sometimes expressed favorable views about the Taliban.
Mateen would spend his youth and young adulthood in Florida, attending a local high school and obtaining an associate’s degree in criminal justice from nearby Indian River State College in 2006, according to college spokeswoman Michelle Abaldo.
Sunday, Omar Mateen dialed Orlando’s 911 service to alert the dispatcher to the carnage unfolding at one of the city’s most popular gay bars.