Several witnesses have claimed Orlando shooter Omar Mateen was a frequent patron of the LGBTI nightclub where he murdered 49 people and injured 53 others on Sunday.

Mateen would “sit in the corner and drink by himself” and other times “would get so drunk he was loud and belligerent”, one of four witnesses told the Orlando Sentinel on Tuesday.

“We didn’t talk to him a lot,” Ty Smith said. “But I remember him saying things about his dad at times. He told us he had a wife and kids.”

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Mateen was killed by police after he shot 49 people dead inside the club and held about 30 hostage for just under three hours.

Mr Smith’s partner Chris Callen, a drag queen at the Pulse nightclub, said he regularly saw Mateen at the nightspot for “at least three years”.

Both stopped speaking to Mateen after he threatened them with a knife, apparently after someone made a joke about religion.

A police handout of killer Omar Mateen. Photo: Supplied

Another witness, Kevin West, told the Los Angeles Times that he saw and eventually met Mateen at Pulse using a gay dating app called ‘Jack’d’ more than a year ago.

Pulse regular Cord Cedeno told MSNBC television: “It was definitely him. He’d come in for years, and people knew him.”

Mr Cedeno said he saw Mateen’s online profile on gay dating apps ‘Grindr’, ‘Jack’d’ and ‘Adam4Adam’.

Later on Tuesday, a male former classmate told the Palm Beach Post that Mateen had once asked him out on a date.

The classmate, who wished to stay anonymous, said he went to gay nightclubs with Mateen while they attended River Community College police academy together.

“He just wanted to fit in and no one liked him,” he said. “He was always socially awkward.”

The gunman’s father, Seddique Mateen, insisted his son was not gay: “It’s not true. Why, if he is gay, would he do this?”

The claims that Mateen was a regular at the club shocked the world, as it comes to terms with exactly what happened during the three hours of hell early Sunday morning (local time).

Here is what the Pulse nightclub looks like from outside, followed by a timeline of what happened during the massacre:

The Pulse nightclub was turned into a bloodbath by Mateen. Photo: Getty

1. Shooter arrives and enters

2:00am Omar Mateen parks his van outside Pulse nightclub.

2:02am Mateen enters club, Orlando police chief John Mina confirmed, armed with an AR-15 semi-automatic rifle, a 9mm handgun and “another device”, reportedly explosives.

2. Shooter begins the massacre

2:03am Resident Marolon Massey, at a nearby apartment block, heard gunshots, Maclean’s reported.

Three hundred people were inside the LGBT club for Latin night. Mr Mina said the gunman fired “numerous shots” and a large yet “unknown number of rounds” into the revellers.

Witness Jackie Smith said scores of people dived to the floor, or fell wounded, while others rushed to escape.

A police officer working “extra duties” at the club exchanged fire with the suspect.

Nursing student Amanda Alvear – one of Mateen’s 49 victims – was on the dance floor and posted a short video to Snapchat of the moment the shots began.

At one point Mateen went outside the club and then returned inside.

2:05am Mr Massey checked his phone as the shots went “pop, pop, pop!”. They ended at 2:05am.

2:06am Eddie Justice, who died in the attack, text messages his mother, Mina Justice: “Mommy I love you. In club they shooting”.

2:09am Pulse nightclub posts chilling message to Facebook: “Everyone get out of Pulse and keep running”.

3. Hostage situation begins

2:17am It’s now clear that a hostage situation had developed inside the club, Mr Mina said. Brandon Wolf tweeted: “Omg. Shooting at pulse. We hid in the bathroom. And we can’t find our friends.”

Eddie Justice perished in the attack, his desperate messages have gone viral.

This forced police to build up a presence around the building and begin negotiations with Mateen.

Ambulances, police bomb units and hazardous materials teams are sent to the scene.

Many hostages hid in the bathrooms and another dance area.

2:39am Eddie Justice texts his mother from the bathroom, pleading for her to call police:

“Call them mommy … Now … He’s coming … I’m gonna die.”

2:42am Mina Justice asks her son if anyone was hurt and which bathroom he was in: “Lots. Yes”.

2:50am Last text Mina Justice received from Eddie Justice. He died in the attack.

3am SWAT team called to scene. Some communication with Mateen, but police would not elaborate.

Mateen made a 911 call at an unknown time where he pledged allegiance to the Islamic State, the New York Times reported.

4. Police storm the building

5am Officers storm building and rescue 30 remaining clubbers, likely in a smaller dance room.

Officers used two explosive devices to distract gunman, then ram a hole in a wall with an armoured vehicle. Eleven officers storm the club.

Police said the hostages ran free through the hole in the wall. The gunman followed. He engaged in a shootout with police and was fatally shot.

5:53am Orlando Police tweet: “Pulse Shooting: The shooter inside the club is dead”.

Fifty people died in the attack, including Mateen. Orlando mayor Buddy Dyer said 39 people were slain in the nightclub, two died outside and nine perished in hospital.

– with ABC and reporting by James Ried