Gunman Omar Mateen, who killed at least 50 people in a gay nightclub in Florida, was mentally unstable and had a history of using steroids, his ex-wife has said.
The 29-year-old wielded an assault-type rifle and a handgun and opened fire inside Pulse, in Orlando. It's the deadliest mass shooting in modern US history.
Mateen was later killed in a shoot-out with police officers after taking hostages.
Police were investigating the attack - which left at least 53 other people in hospital, most of them critically ill, leading to fears the death toll would rise - as an act of terrorism.
Mateen made a 911 call from the club in which he professed allegiance to the leader of Islamic State, Abu Bakr al-Baghdadi, a law enforcement official said.
Sitora Yusufiy said to reporters in Boulder, Colorado, that she was with Mateen for only four months because he was abusive and that they had no contact for the last seven or eight years.
Mateen was short-tempered and had a history with steroids, she also said.
Yusufiy described him as religious but not radical, and said he wanted to be a police officer and applied to a police academy.
"He was mentally unstable and mentally ill," she said.
Mateen would not let her speak to her family, and relatives had to come and literally pull her out of his arms, she said.
Yusufiy said she was "devastated, shocked, started shaking and crying" when she heard about the shooting, and she attributed the violence to his mental illness, not any alliance with terrorist groups.