Orlando shooter Omar Mateen angered seeing gay couple kissing?

Omar Mateen, the mass murderer with an Afghan descent who gunned down 49 people in an Orlando nightclub Sunday, June 12, may have been set off by seeing a same-sex couple kissing each other.

Seddique Mir Mateen, the gunman's father, thinks that his son may have been enraged when he saw two men kissing each other.

He told NBC News, "We were in downtown Miami, Bayside, people were playing music. And he saw two men kissing each other in front of his wife and kid, and he got very angry."

"They were kissing each other and touching each other, and he said: 'Look at that. In front of my son, they are doing that.' And then we were in the men's bathroom, and men were kissing each other," he added.

Considered as the deadliest mass shooting in U.S. history, authorities are investigating the motive behind the hostage crisis that lasted about three hours and only ended when the Special Weapons and Tactics (SWAT) team stormed the Pulse nightclub with an armored vehicle and gunned down 29-year-old Mateen. A total of 49 were killed while 53 were injured.

Mateen had called 911 and pledged to ISIS before the shooting rampage, according to official reports. However, law enforcement officials say there's no indication of direct contact between Mateen and ISIS.

Mateen's family insists religion has nothing to do with the incident, pointing instead to Mateen's pure hatred against the lesbian, gay, bisexual, and transgender (LGBT) community as the main cause. However, by Monday night claims were emerging that Mateen had been visiting the Pulse gay nightclub for numerous years prior to the shooting.

The gunman, who worked as a security guard at G4S Secure Solutions, had anger management issues and was easily set off by women, race or religion, said his co-worker Daniel Gilroy.

Gilroy added that Mateen "always referred to every other race, religion, gender in a derogatory way."

Sitora Yusufiy, who left Mateen four months into their marriage because of abuse, told ABC News he was a "sick person" who went "really confused" and "crazy."

Ronald Hopper, FBI Assistant Special Agent, revealed that Mateen had been interviewed by the FBI in 2013 and 2014 for inflammatory remarks.

"Those interviews turned out to be inconclusive, so there was nothing to keep the investigation going," said Hopper, as reported by CNN.