ORLANDO • Nightclub shooter Omar Mateen appears to have been an angry, violent man who laughed as he carried out America's deadliest mass shooting.

Pastor Deyni Ventura visited a survivor in hospital, whom she identified only as Norman, who had taken refuge in a bathroom stall crammed with 30 people.

Norman could hear the shooter laughing loudly as he sprayed gunfire over and under the bathroom stall. "They couldn't see the shooter but they could hear him laughing," Ms Ventura said.

And The Washington Post reported that, according to some of Omar's former Florida high school classmates, he had celebrated as students watched the horrors of Sept 11, 2001 unfold on live TV. He had "started jumping up and down cheering on the terrorists", one said on a Facebook group chat.

Omar's former wife, Ms Sitora Yusifiy, described him as mentally unstable and violent towards her.

"He would get mad out of nowhere. That's when I started worrying about my safety, and then after a few months, he started abusing me physically very often," she told reporters. The couple split in 2009 after four months of marriage.

When Omar met his father the day before the killings, he betrayed nothing of the rage that would soon erupt.

"I didn't notice anything wrong," Mr Seddique Mateen said in an interview. "He was very slick."

In the close-knit Muslim community of about 100 families in Fort Pierce, Florida, Omar was known as a quiet person with few friends.

"He wasn't a people person. He was not extremely friendly but he wasn't rude either," said Mr Mohammed Jameel, 54, who worshipped at the same mosque as Omar.

REUTERS