Gunman had been investigated and cleared by FBI on two occasions
The man behind the worst mass shooting in US history has been described as a wife-beater and steroid-taking 'sleaze' who hassled girls in his gym and was investigated by the FBI for connections to a Syrian suicide bomber.
Omar Mateen (29) had worked since September 2007 as a security guard in Florida with the British-based security company G4S, which is tasked in the US with protecting federal buildings.
Last night, questions were being raised as to how a man with his violent past and suspected radicalism had been employed as a guard and given access to weapons.
He was born in New York to Afghan parents and at one point was married to a woman in New Jersey.
"He was not a stable person," said the ex-wife, who spoke to the 'Washington Post'.
"He beat me. He would just come home and start beating me up because the laundry wasn't finished or something like that."
Tim Crownover, who lives near Mateen's home in Fort Pierce, Florida, said a friend told him Mateen was a bodybuilder who used to be a "huge creep" toward girls.
"Everybody thought he was on steroids, I guess," Mr Crownover said.
Mateen had come onto the FBI's radar twice - first in 2013, when he made inflammatory comments to colleagues about terrorism, said Ronald Hopper, from the FBI.
He was interviewed and investigated, but was not considered to be a threat.
A year later, the FBI interviewed him again, in connection with Moner Mohammad Abusalha, the first American to carry out a suicide attack in Syria in May 2014.
After training, Abusalha returned home to Fort Pierce for several months in 2013.
Law-enforcement officials say he tried to recruit others to go back to Syria.
Mateen had a licence for the concealed carrying of a weapon and also had a licence to work as a security guard.
The gay club was deliberately chosen, his father, Mir Seddique, said.
"We are apologising for the whole incident," he added.
"We weren't aware of any action he is taking. We are in shock, like the whole country."