A police officer who was one of the first to arrive at the Pulse nightclub in Orlando has claimed he was made to wait while Omar Mateen wandered around the club gunning people down.

The FBI said this week that police first responders 'engaged the shooter' inside the club at 2.08am but Officer Brandon Cornwell said he had been told to wait for a SWAT team to arrive.

It is known that Mateen, who was heavily armed with an AR-15 assault rifle and a handgun and was feared to be carrying explosives, had an exchange of fire with a security guard when he first arrived at the LGBT club, which was holding its regular Latino night.

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Attorney General Loretta Lynch (right) visited Orlando yesterday and praised the actions of first responders at the Pulse nightclub massacre

Five or six Orlando cops arrived on the scene within minutes, broke through a large glass window and entered the club as Mateen hunted down victims inside.

Officer Cornwell, 25, told the Washington Post he was one of those police first responders and has given an account of the terrifying moments as they waited for orders outside the darkened club.

He said: 'There was tons of people running out of the club. I grabbed my assault rifle and ran toward the club. At this point, the shooter is still actively shooting inside.'

ORLANDO SHOOTINGS TIMELINE 2:02am - Sunday, June 12 - Suspect Omar Mateen tries to enter Pulse nightclub armed with assault rifle and and handgun and is spotted by a security guard. The two exchange fire outside the club - but Mateen manages to enter the nightclub, holding 320 people, while still firing. First 911 call received by Orlando Police Department. 2:04am - First police officers, including Brandon Cornwell, arrive at the scene. 2:08am - FBI says officers entered the club and 'engaged' the shooter. 2:09am - Pulse nightclub posts a message to their Facebook desperately telling those inside 'Everyone get out of pulse and keep running'. 2:35am - Mateen calls 911 and pledges allegiance to ISIS and Abu Bakr al-Baghdadi. 4:21am - Police rip out an air conditioning unit, creating a hole through which some people escape. 4:29am - Rescued victims tell police the shooter said he was going to put four vests with bombs on hostages within 15 minutes. 5.02am - Three hours after the first shooting began, a SWAT team use armored vehicle and explosives to breach the bathroom wall. SWAT officers manage to free 30 hostages who dashed to safety. 5:15am - The shooter is shot at and is confirmed as being 'down'. 8:00am - Officials with the FBI deem the incident to be 'domestic terrorism'. 9:40am - The shooter was officially identified as 29-year-old Omar Mateen of Port St. Lucie. 10:20am - At a press conference Mayor Buddy Dyer makes the announcement that 49 people have died and 53 injured in what is now the worst mass shooting in the history of the United States. 11.54am - US Senator Bill Nelson and California congressman Adam Schiff claimed Mateen had pledged his allegiance to ISIS Advertisement

The officer said: 'We were trying to locate exactly where the shooter was - we kept hearing people scream and shots fired.'

Cornwell said they eventually entered and went to the bathroom area, where Mateen had taken hostages and appeared to be preparing for a final stand.

'He was actively shooting. I can't say if he was targeting us. But he was still shooting in that location where he was at. There were bullet holes in the wall, so he had shot through the wall. But I couldn't tell you if he was shooting at us,' he said.

Children write messages for the victims of the Pulse Nightclub shooting at a makeshift memorial at the scene. The memorial is decorated with a Puerto Rican flag as many of the victims were originally from Puerto Rico

But Cornwell said they were told by their commanders not to enter the bathroom until the SWAT team arrived.

He said they waited '15 or 20 minutes' or possibly more until the SWAT team arrived, he said.

Cornwell said: 'We just basically stayed there, waited for movement, and we just held our position until SWAT got there.

Investigators from the office of the medical examiner at the site of the shooting. The holes were made by the SWAT team as they broke in from outside and rescued people from the bathroom area

'Once SWAT got there, they told us to retreat, that they'd take over because we were not really in tactical gear - we were just in our police uniforms.'

Cornwell said he never fired a shot or saw Mateen, who was eventually killed by the SWAT team after he walked out into the parking lot through the hole in the wall created by a BearCat armored vehicle.

His account is the first from a police officer who was inside the club but he said he could not go into too much detail because of the ongoing investigation.

FBI agents and police are pictured outside the club in the aftermath of the shooting. The FBI has said the shooter was 'engaged' at 2.08am but it is not known if that means officers shot at him

Some clubbers were rescued shortly after the attack began, and others at 4.21 am but most were not freed until 5am.

It is not clear how many people were killed by Mateen while police officers were at the scene.

Mateen swore allegiance to ISIS before killing 49 people at Pulse and claimed to be a Muslim but he is thought to have been acting out of homophobia, and possibly out of a deep sense of self-loathing because he himself was gay.

Loretta Lynch was joined by the Mayor of Orlando, Buddy Dyer, as she visited wreaths commemorating each of the 49 victims of the shooting

The Attorney General Loretta Lynch visited Orlando yesterday and said they had not yet found the 'magic bullet' to stop people being brainwashed by jihadist propaganda.

But she said of Mateen: 'While we know a lot more about him in terms of who he was and what he did, I do not want to definitively rule out any particular motivation here.

'It's entirely possible that he had a singular motive. It's entirely possible that he had a dual motive.'