Sunday afternoon, FBI investigator Ronald Hopper told members of the press that the Orlando shooter Omar Mir Seddique Mateen, who was responsible for over 50 deaths at a gay nightclub, was previously investigated on two separate occasions. 

Hopper said: 

The FBI first became aware of Mateen in 2013, where he made inflammatory comments at co-workers alleging possible terrorist ties. The FBI thoroughly investigated the matter, including interviews with witnesses, physical surveillance and records checks. In the course of the investigation, Mateen was interviewed twice. Ultimately, we were unable to verify the substance of his comments and the investigation was closed. 

The investigator also stated that in 2014, Mateen again came to the attention of the FBI because of possible ties with to an American suicide bomber, where they interviewed Mateen and determined that the contact was minimal and did not constitute as a threat at the time. 

In Sunday press conference Hopper confirmed that Mateen, an American citizen from Port St. Lucie, Florida, did in fact make a 911 call before the shooting swearing allegiance to ISIS.