Haunting new images reveal Thomas Crooks scoping out the grounds around Donald Trump's rally before 'bear-crawling' onto the rooftop

A haunting new video shows Donald Trump's would-be assassin lurking around the grounds of the rally approximately an hour before the shooting took place. 

The new clip, first reported by WTAE in Pittsburgh, sees Thomas Crooks, 20, walking alone, far from the rest of the fervent crowd, who waited in the baking sun to see the ex-president speak on July 14 in town of Butler. 

Crooks is seen close to a building just outside of the secure perimeter at 5:03 pm. The crazed gunman opened fire on Trump at 6:11 pm, wounding the Republican nominee in the ear and killing retired fire chief Corey Comperatore.

When he's first seen in the video, Crooks is walking in a direction away from the crowd passed a warehouse. The camera pans away from him for a few seconds and then catches him again, this time he's standing in place, looking up at something.

This video is the latest illustration of Crooks' bizarre behavior prior to the attempted assassination that only piqued the interest of the Secret Service minutes before the attack. 

By the time a photo of Crooks was circulated to officers around 5:40pm, security had lost track of him, allowing him to take up a position on top of the American Glass Research building and open fire.  

In the first clip showing Crooks, the gunman is seen walking near some buildings just outside of the security perimeter 

When he's seen again, Crooks appears to be looking upwards at something 

The man who recorded the video told the station that he was merely trying to capture the crowd size. It was only when he reviewed the clip after the shooting did he notice was recording the shooter. 

'I wanted to pan the crowd because it was a massive crowd, so I was just taking in the moment. So this was before the shooting. Obviously had no idea how that day, how that day would end,' the unnamed man said.

'When I saw the video last night, when I was going back through my my video clips and saw him, I was chilled to the point where I couldn't fall asleep right away... 

At the time the video was taken, Crooks had already been flagged as suspicious by law enforcement. By the time two police officers walked over to check him out, he was on the roof, belly crawling.

'He's got a gun,' a bystander yelled. I didn't sleep well. There's - there's something. Something really went wrong with this,' he said. 

One officer hoisted the other to the lip of the roof. As the officer pulled his head over the edge, a long-haired young man wearing glasses turned toward him, wielding an AR-15 -style rifle. The officer dropped back to the ground, the Butler County sheriff said. 

Crooks, an introverted 20-year-old computer whiz who had just earned a spot at a college engineering program, turned back to his target about 400 feet away. 

He squeezed off several shots at Trump, clipping the former president's ear, killing an audience member and wounding two others before Secret Service snipers on a nearby building killed him with counterfire.

Trump was wounded in the ear but still turned to the crowd and said: 'Fight!'

This account of the first assassination attempt to injure a U.S. president since 1981 is based on interviews with more than two dozen people, including law enforcement officials, Crooks' school associates and witnesses who attended the rally, along with public records and news accounts.

Crooks fired his rifle at approximately 6:10 pm, according to a Reuters photographer at the rally. Trump winced and grabbed his right ear. Secret Service agents tackled the former president and some supporters dived for cover. 

A bullet hit what appeared to be the hydraulic line of a forklift that held a bank of speakers to the right side of the stage. Fluid spewed across the crowd and the lift's arm collapsed. To the left, screams erupted where a spectator had been fatally shot. 

As Secret Service agents tackled the former president, some supporters scrambled for safety. Others grabbed children and hustled towards the gates.

'The audience wasn't like what you'd expect out of a crowd that just experienced something like this,' said Saurabh Sharma, a Trump supporter sitting near the front. 

'Everyone was really quiet. There were a few women crying. They were, you know, saying, 'I can't believe they tried to kill him.' 

Four days after the assassination attempt, a coherent picture of the moments before the shooting was emerging. But Crooks' ideology and reasons for pulling the trigger remained a mystery.

A review of Crooks' phone by the Federal Bureau of Investigation found he had searched for images of both President Joe Biden and Trump, as well as other famous figures, in the days before the shooting, the New York Times reported on Wednesday, citing U.S. lawmakers briefed on the law enforcement investigation.

Crooks had been searching for the dates of Trump's public appearances and of the Democratic National Convention, the report said. He had also looked up 'major depressive disorder' on his phone, the Times said. 

Crooks appeared to spend at least some time preparing for the Trump event. 

He bought ammunition on the day of the rally, stopping at a gun store in his hometown of Bethel Park to pick up 50 rounds, according to a joint bulletin issued this week by the Department of Homeland Security and the Federal Bureau of Investigation, which is leading the investigation.

He built three homemade bombs – two found in his car and another in his home, according to the bulletin. 

In the preceding months, the bulletin noted, Crooks had received 'multiple packages, including some marked as possibly containing hazardous material.'

At the rally, Crooks caught the attention of local law enforcement while pacing around the grounds before Trump took the stage. 

One officer called in a report of a suspicious person and snapped a photo that was distributed electronically to other officers at the scene, according to Butler County Sheriff Michael Slupe, a Trump backer who was seated near the front of the rally as a special guest.

As two Butler Township Police officers responded to the call, people in the crowd already had noticed a man on the roof.

Slupe told Reuters the officer who initially pulled himself onto the roof had no time to unholster his gun when Crooks turned on him, leaving him no option but to drop back to the ground.

Secret Service officials have said their agency is responsible for securing the area within the event's security perimeter.

The building used by Crooks was just outside it. But some former agency officials and other security experts have disputed that contention, arguing that buildings with a direct sight line and within firing range of the former president should have been swept and under constant surveillance by the service's sniper teams.

Local officials have bristled at any suggestions that town or county law enforcement was responsible for securing the building.