A man claiming to be Orlando gunman Omar Mateen's former gay lover has said he had a vendetta against homosexual Puerto Ricans who "rejected him".

The man, speaking under the pseudonym 'Miguel', said he met Mateen on gay dating app Grindr and soon became friends-with-benefits with the gunman, who shot dead 49 people at a Latin-themed event at Pulse nightclub on 12 June.

Mateen, who is believed to have made a call to the emergency services during the massacre and pledged his allegiance to a number of conflicting groups, was also allegedly spotted in the gay nightclub several times before the massacre.

Miguel said he felt rejected by gay Puerto Ricans and blamed them for an HIV scare he had a year previously, when one of two men he had slept with revealed he was HIV positive.

"He was terrified that he was infected," Miguel said in an interview with Latin American news service Univision translated by Mediaite in which Miguel wore prosthetics to disguise his appearance.

"I asked him, 'Did you do a test?' Yes. He went to the pharmacy and did the test ... it came out negative but it doesn't come out right away. It takes four, five months."

"He adored Latinos, gay Latinos, with brown skin – but he felt rejected. He felt used by them – there were moments in the Pulse nightclub that made him feel really bad. Guys used him. That really affected him," Miguel continued. "I believe this crazy horrible thing he did – that was revenge."

Miguel is also believed to have been interviewed by the FBI as part of their ongoing investigation into the massacre, and has joined a growing number of people claiming the shooter was a gay man struggling with his sexuality.

Omar Mateen
Omar Mateen, who carried out the mass shooting at the Pulse nightclub in Orlando Reuters