Thomas Crooks pictured almost an hour before he shot Trump: Sniper identified gunman acting suspiciously checking his cell phone and a rangefinder at rally when they took photo

Security service officials had would-be assassin Thomas Matthew Crooks on their radar for more than 40 minutes before he shot Donald Trump, a new image reveals. 

A photograph showing the 20-year-old gunman appearing to crawl on the ground while scouring the area was circulated to law enforcement as a suspicious sighting at 5:30pm during the Butler, Pennsylvania rally on July 14, according to WPXI. 

Around 6.11pm, Crooks took up a position on a slanted warehouse roof and shot at Trump from a distance of around 165 yards, wounding him in the ear and killing retired fire chief Corey Comperatore. 

Two more newly-released images also show a bicycle owned by Crooks which was recovered close to the scene, and a remote detonator which was recovered from his dead body alongside his cellphone. 

It was later revealed that the detonator was connected to explosives found in his car.

The latest revelations bring more questions to the fore about the Secret Service handling of the event - after embattled boss Kimberley Cheatle bizarrely said officials considered the roof to be too risky a position to station an agent.

A photograph (above) showing the 20-year-old gunman appearing to crawl on the ground while scouring the area was circulated to law enforcement as a suspicious sighting at 5:30pm during the Butler, Pennsylvania rally on July 14, according to WPXI 

Police personnel stand over Crooks body on the rooftop of America Glass Research, located just a couple of hundred yards from where Trump was speaking on Saturday

Another newly-released image also show a bicycle owned by Crooks which was recovered close to the scene

Another fresh image shows a remote detonator which was recovered from Crooks' dead body alongside his cellphone. It was later revealed that the detonator was connected to explosives found in his car

The gunman was also acting strangely around the metal detectors that attendees were forced to walk through before entering the event grounds. Witnesses said that Crooks was furiously checking his phone and operating a hunting range finder.

He attempted entry around this point but set the detector off and was refused, sources said. 

Around 5:30pm, the picture of Crooks crawling on the ground was circulated to various members of the Secret Service after reports about his suspicious behavior were made to security. 

Crooks is seen wearing glasses and a t-shirt with the logo for popular YouTube channel Demolition Ranch.

At some point, officers lost track of Crooks. He was next seen climbing to the roof of the American Glass Research building. Around seven minutes later, he opened fire on Trump.   

Trump took to the stage at 6:03pm, an hour behind schedule. The gunfire rang out at the venue approximately 6:11pm.   

Trump grabbed his right ear as the first shots rang out at 6:12pm 

Along with the ammunition that he purchased, Crooks also bought a ladder at Home Depot earlier the same day.

In the wake of the shooting that killed one spectator, investigators were hunting for any clues about what may have drove Crooks, a resident of Bethel Park, Pennsylvania, to carry out the shocking attack. 

The FBI said they were investigating it as a potential act of domestic terrorism but the absence of a clear ideological motive by the man shot dead by the Secret Service led conspiracy theories to flourish. 

Investigators believe that he acted alone and have confirmed that there is no social media presence that would indicate that Crooks' attack was politically motivated. 

 Butler County Sheriff Michael Slupe told the AP that a local officer climbed to the roof and encountered Crooks, who saw the officer and turned toward him just before the officer dropped down to safety. 

Slupe said the officer couldn’t have wielded his own gun under the circumstances. 

There two counter sniper teams set up to monitor any threats against Trump 

This 2021 photo provided by Bethel Park School District showsThomas Matthew Crooks

The officer retreated down the ladder, and Crooks quickly took a shot toward Trump, and that’s when Secret Service snipers shot him, according to two officials who spoke to AP on condition of anonymity to discuss an ongoing investigation.

WPXI said multiple sources on Tuesday confirmed that Crooks was on the roof with a gun for fewer than seven minutes before he was confronted by a Butler Township police officer. 

Crooks used an AR-style rifle, which authorities said they believe was purchased by his father. 

The roof where Crooks lay was less than 150 meters (164 yards) from where Trump was speaking, a distance from which a decent marksman could reasonably hit a human-sized target. 

That is a distance at which U.S. Army recruits must hit a scaled human-sized silhouette to qualify with the M-16 rifle. 

Alongside the explosives in his car, investigators also recovered a bullet proof vest and hundreds of rounds of ammunition, which had been purchased, alongside a ladder, on the same day as the shooting. 

From the 'normal little boy' who liked to play soldiers and miniature golf, to the increasingly disturbed young man who grew his hair long and isolated himself from friends

Crooks, known as Tom to his family, grew up in the Bethel Park suburb where his family still live with his parents and older sister, the family home is seen here

Another bulletproof vest, and third remote-controlled bomb was later discovered at the house he shared with his parents.

The latest revelation that a transmitter was also with him has raised fears that Crooks may have been planning to continue his killing spree if he had escaped from the roof with his life, and may have had an accomplice to help him.

Hours earlier Crooks had asked his boss for the day off, telling him he had 'something to do', before travelling to Saturday's rally.

The would-be assassin told colleagues at the Bethel Park Skilled Nursing and Rehabilitation Center that he would see them on Sunday.

But a Secret Service agent at the Butler rally ensured that he would be the last person Crooks saw as he locked eyes with the killer before shooting him dead, graphic video has revealed.

Video shows Crooks peering intently through the sights of his father's AR-style weapon and firing towards the rally as onlookers scream from the base of the building.

Cheatle is already facing calls to step down amid what some are calling a 'massive security failure'

Bullets fired from a manufacturing building roof, right, into the rally, seen left, show just how close Crooks had managed to get the former president

Instantly a second volley of shots is heard and Crooks is pictured lying dead on the roof as those on the ground gasp in horror.

'The Secret Service don't f*** around man,' one exclaims. 'Holy s***.'

He had clambered up building's air conditioning system and hoisted himself onto the roof where MAGA fans saw him 'bear-crawling' across the sloping surface with his rifle, and warned law enforcement of the danger.

'I'm thinking to myself 'Why is Trump still speaking, why have they not pulled him off the stage?,' one witness told the BBC. 'The next thing you know, five shots ring out.'

Crooks was a dietary aide at Bethel Park Skilled Nursing and Rehabilitation Center - where he provided food and care for post-hospital elderly and sick people.

'We are shocked and saddened to learn of his involvement as Thomas Matthew Crooks performed his job without concern and his background check was clean,' administrator Marcie Grimm said in a statement.

A colleague at the facility said Crooks never expressed political views at work and wasn't a 'radical'.

'It's hard seeing everything that's going on online because he was a really, really good person that did a really bad thing, and I just wish I knew why,' he added.

The would-be assassin was a registered Republican and 2022 high school graduate. Records show he donated on the day of the 2020 inauguration to a progressive group backing President Joe Biden.

A chance turn of Trump’s head, not the swift response of those snipers, is what made the difference between a grazing glance of the bullet Crooks fired and a fatal shot

He graduated from the Community College of Allegheny County in May with an associate degree in engineering science, according to school officials who said they were 'shocked and saddened by the horrific turn of events'.

Crooks' father Matthew was seen on Tuesday morning for the first time since the shooting as he opened the door of the family home to FBI agents.

A neighbor of Crooks' sister Katie said her brother helped her move into her nearby apartment three years ago, describing her as a 'hardworking' woman who worked as a janitor at a local high school and as a server at a restaurant.

Both of Crooks' parents are behavioral therapists and Crooks' father said he was baffled by his son's actions.

The Justice Department, the Secret Service and the FBI, are due to brief senators about the investigation on Wednesday Majority leader Chuck Schumer revealed on Tuesday night as the Secret Service faces intensive scrutiny over its handling of security at the rally.