Gunman Behind Orlando Nightclub Shootings Was Investigated by FBI Twice

Omar Mateen was interviewed for having possible ties to ISIS

Photo: Source: Omar Mateen/Myspace

The gunman behind the Orlando nightclub shootings, the deadliest mass shooting in American history, had been investigated by the FBI on two separate occasions for his possible ties to Islamic extremism.

According to the FBI press conference, Omar Mateen was interviewed prior to the June 12 shooting that left at least 50 dead and at least 53 more injured.

The first investigation occurred after Mateen made concerning comments at work. As part of their investigation, the FBI interviewed witnesses, provided physical surveillance, and interviewed Mateen on two separate occasions, but the investigation was ultimately closed.

In 2014, the FBI opened a second investigation into Mateen for his ties to Moner Mohammad Abu-Salha, a Florida born Jabhat al-Nusrah (sometimes known as “al-Qaeda in Syria”) supporter who blew himself up in Syria in August 2014. Abu-Salha appeared in a 22-minute video in which he mentions being surveilled by the FBI prior to leaving for Syria. Mateen was interviewed as part of the investigation, but there was not enough evidence at the time and the case was closed.

A federal law-enforcement official tells PEOPLE, “The FBI was aware of this guy before today. He was on their radar.”

According to police, Mateen opened fire just after 2 a.m. local time at Pulse, a popular gay club south of downtown Orlando. An officer working at the club initially responded to the shooter, “engaging in the gun battle with the suspect” before the suspect went back into the club, Orlando Police Chief John Mina said at a Sunday morning news conference.

The shooter held several people hostage for several hours. At 5 a.m., police moved in to rescue the hostages. More gunshots followed, and police also used explosives in an attempt to distract the suspect. Eventually, Omar Mateen was shot and killed.

The gunman called 911 approximately 30 minutes after opening fire at Orlando’s Pulse, a federal law enforcement official tells PEOPLE. On that call, he announced he was shooting up the club and claimed he was armed with explosives a claim which authorities have not confirmed and which they are “still exploring,” the official says.

“The 911 operator, using reverse-call technology, called back the gunman and it was then that he pledged allegiance to [ISIS leader] Abu Bakr al-Baghdadi,” the federal official tells PEOPLE. The gunman “also mentioned the Tsarnaev brothers,” who orchestrated the Boston Marathon bombings of 2013, the official says.

ISIS also claimed responsibility for the attack.

“Agents in Afghanistan are looking at the shooter’s connections there,” an FBI source with knowledge of the investigation tells PEOPLE. “He has family there. This is not to say his family is connected to the shootings. This is the normal course of an investigation like this. We ask questions.”

“The Islamic State called for attacks on the West during Ramadan,” the source continues. “In the wake of San Bernardino, we are very much mindful of how this can play out.”