How on earth did a gunman who was acting suspiciously crawl onto the roof of a building 130 yards away from where former president of the United States was speaking and manage to fire at least eight shots before he was taken down?

That is just one of the damning and terrifying questions that are unanswered after the assassination attempt on Donald Trump that is being described as an enormous security failure.

Terrifying new video from TMZ has captured the moment Thomas Matthew Crooks of Bethel Park, Pennsylvania, lay down on the roof of a nearby building, in full view of horrified Trump supporters, and fired towards the stage.

Crooks killed former volunteer fire chief Corey Comperatore, who was sat in the bleachers and died a hero protecting his family, and then hit Trump in the ear.

He was spotted and then watched by law enforcement at the Trump rally site because they sensed something wasn't right, according to reports. But then they lost sight of them before the carnage unfolded.

Witnesses say they warned cops about a man armed with an AR-style rifle climbing on top of a building, but he was still able to open fire.

Why were the alerts ignored? Why did the Secret Service fail to fully protect a former president and presidential candidate just four months from the election? 

Terrifying video captures the  moment Thomas Matthew Crooks opened fire at Donald Trump during his rally on Saturday night. He shot the former president in the ear and then killed a member of the crowd

Terrifying video captures the  moment Thomas Matthew Crooks opened fire at Donald Trump during his rally on Saturday night. He shot the former president in the ear and then killed a member of the crowd

There are also questions of why the surroundings weren't fully surveyed. 

The Secret Service's primary responsibility is to protect current and former presidents, a job they have been accused of failing spectacularly. 

It is perhaps the worst lapse in security since President Ronald Reagan was shot and wounded at a Washington hotel in 1981. 

They now face a torrent of questions of how the first assassination attempt in 43 years was allowed to happen. 

Politicians, law enforcement and critics are demanding answers on how Crooks managed to get so close to a rally that was surrounded by such vast security. 

Top Republicans and Democrats have demanded an urgent investigation. 

Police stand over the body of Donald Trump gunman Thomas Matthew Crooks after he was shot and killed by Secret Service 

Witnesses say they warned cops about a man armed with an AR-style rifle crawling on a roof and getting into a prone position, but he was still able to open fire

Witnesses say they warned cops about a man armed with an AR-style rifle crawling on a roof and getting into a prone position, but he was still able to open fire

There are suggestions that routine checks would have eliminated all potential threats.

In a damning statement on Saturday night, FBI Special Agent Kevin Rojek said it was 'surprising' Crooks managed to fire off so many shots.

There are also allegations that Trump's team asked for more protection on the campaign but was rebuffed.

The Secret Service has since denied those claims, but are still under immense scrutiny for what has been called an 'absolute failure'.

And Rep. Tim Burchett, R-Tenn., became the first lawmaker to say that the director of Secret Service Kimberly Cheatle 'needs to go.' 

President Joe Biden, addressing Americans from the White House Sunday, promised an 'independent review' into what happened at the rally.

'I'm directing an independent review on national security [at] yesterday's rally to assess exactly what happened, and we'll share the results of that independent review with the American people as well,' Biden stated.

Former Secret Service agent Joseph LaSorsa said there will be an 'intensive review' and 'massive realignment' in the agency. 'This cannot happen' he said.

He told DailyMail.com that it was very lucky Trump turned his head at the last second so the bullet only hit his ear.

He said that protection needs to be upped for former presidents and Trump will now almost have the same protection as President Joe Biden.

But there are questions of why a man targeted by so many did not have a sufficient level of agents around him.

He also explained why agents from the under fire agency may not have been able to see the gunman. 

'Remember they’re observing 360 and you’re dealing with seconds. They’re monitoring maybe in that case it might have been 240 degrees. 

'They’re looking at many areas and it only took seconds for that individual to get up there and luckily he was a 20 year old and not a superior marksman. 

'Luckily for all of us as a country that he was only 20.'

He added: 'Had he not been taken out he would have been able to continue reshooting. 

'The fact that there was a counter sniper team that took him out is quite fortuitous and very lucky for the country, because this could have been a thousand times worse.'

Trump raises his fist below the American flag, with blood across his face, moments after the shooting

Trump raises his fist below the American flag, with blood across his face, moments after the shooting 

Blood is seen coming from Donald Trump's ear, where he said he was shot

Blood is seen coming from Donald Trump's ear, where he said he was shot

Steve Nottingham, a former SWAT commander in Long Beach, California, told NBC News that the shooting was a 'fundamental security failure'.

Jim Cavanaugh, a retired special agent in charge with the Bureau of Alcohol Tobacco and Firearms (ATF) was stunned the shooter got so close.

Greg Smith who owns Brenckle's Farms & Greenhouses, told DailyMail.com he saw the would-be assassin climb onto the top of a building, and that he was bewildered by the lack of action from agents.

'I'm thinking to myself, "Why is Trump still speaking on this stage right now? Why is he still up there talking?" he told DailyMail.com.

After the gunman opened fire he saw the Secret Service 'blow his head off,' the man said in a video captured by the BBC. 

'I saw Secret Service blow his head off,' he said, and then ran to collect his wife and three kids and return to safety.

'At this point, I'm feeling, as I think about it more and more, it just feels like a huge security failure to me,' he told DailyMail.com.

'This isn't a big place, there's not a lot of buildings around here, why is everything not covered.'

He said he had spotted a guy crawling up on the roof of a building.

'I noticed there's a guy crawling up the roof of that building,' he continued to DailyMail.com. 'I'm like, 'that doesn't seem right.'

He said the man definitely did not look like Secret Service, wearing tan and grey clothes, and was not in uniform.

Spotted police officers running around the building, appearing to be looking for someone.

'I'm pointing at the roof, like, "Hey man, there's a guy on the roof with a rifle."'

Agents then climbed onto the roof, where the gunman was and images from social media appeared to show a man lying lifeless.

The witness, a Trump supporter, told the BBC how he had seen the shooter prepare to assassinate the former president.

Questioned why there was no one in the water tower that overlooks the whole property he replied: 'I don't like it man, I don't like what's going on, I don't like what it feels like, I really don't.'

Other rally attendees also saw him on the roof for three or four minutes with no action taken by law enforcement, he said.

An extraordinary photo shows Donald Trump on the ground at Butler Show Grounds in Pennsylvania Saturday after he was injured in a shooting that left two people dead

An extraordinary photo shows Donald Trump on the ground at Butler Show Grounds in Pennsylvania Saturday after he was injured in a shooting that left two people dead 

He said: 'We noticed a guy crawling, you know army, bear crawling up the roof of the building 50ft away from us.

'So we are standing there pointing at the guy crawling up the roof, he had a rifle, we could clearly see he had a rifle.'

The Secret Service has rejected claims the former President Donald Trump was denied additional protection before the attempted assassination as the agency faced mounting questions over the failure in security.

Secret Service spokesman Andrew Guglielmi hit back at 'untrue' allegations from Republicans and members of the former president's inner circle that requests for a bigger security detail were rebuffed.

'There's an untrue assertion that a member of the former President's team requested additional security resources & that those were rebuffed,' Guglielmi wrote on X on Sunday morning, responding to Trump supporters and online claims. 

'This is absolutely false. In fact, we added protective resources & technology & capabilities as part of the increased campaign travel tempo.'

House Republicans plan to bring Secret Service head Kimberly Cheatle for what is expected to be heated questioning on July 22, as lawmakers demand answers.

'I have already contacted the Secret Service for a briefing and am also calling on Secret Service Director Kimberly Cheatle to appear for a hearing. The Oversight Committee will send a formal invitation soon,' said House Oversight chairman Rep. James Comer of Kentucky.

The suspected shooter came within inches of killing the former president, who was wounded in the ear and hurried away from his Pennsylvania speech venue by Secret Service agents.