The US Department of Justice has defended the Federal Bureau of Investigation (FBI)'s previous investigations of Omar Mateen, the suspect in the Orlando nightclub shooting that left dozens of people dead last week.
US Attorney General Loretta Lynch, the head of the Justice Department, said on Sunday FBI investigators found no indications of terrorist inclinations before Mateen shot dead 49 people and injured 53 others in Orlando, Florida, on June 12.
"This is about two years ago, and I can assure you, had he indicated he was going to take action, that they would have stayed on that investigation," Lynch told ABC News.
"At the time, the FBI did everything it could to see if he was about to carry out anything,” she added.
According to an intelligence official, the FBI first noticed Mateen, a US citizen of Afghan descent from Port St. Lucie, Florida, in 2013 when he made "inflammatory comments to coworkers alleging possible terrorist ties."
The agency interviewed him twice in the course of that investigation but it was unable to verify the substance of his comments.
The FBI again carried out an investigation into possible ties between Mateen and a US suicide bomber in 2014. The agency interviewed Mateen again but determined that the contact did not constitute a threat at that time.
The FBI said it is investigating both domestic and international connections to the mass shooting that was reportedly claimed by the Daesh terrorist group.
Mateen, who died in a shootout with police, purportedly praised the Daesh (ISIL) terrorist group during the killings.
The Daesh Takfiri group, which was initially created and funded by the US and its regional allies to destabilize the Middle East region, particularly Syria, has reportedly claimed responsibility for the Orlando shooting. The group now controls large parts of Iraq and Syria.