Within minutes, what should have been a regular rally for Donald Trump quickly spiraled into a deadly assassination attempt in Pennsylvania.
Using videos from the ground and aerial imagery, Sky News details what we know about the security efforts before and during the attack.
Our analysis found police vehicles were parked as close as 20m/65ft away from the gunman and members of the crowd had spotted the shooter on the roof of a building two minutes before shots were fired at the former president.
As questions remain for the Secret Service, former senior executive from FBI counterterrorism Christopher O’Leary said they were presented with a “challenging mission” but were “ultimately responsible” for protecting Trump and the crowd.
Sniper teams in position before event starts
Trump’s campaign rally took place on Saturday evening at the Butler Farm Show, around 50km/30 miles north of Pittsburgh.
Footage filmed of the crowds an hour before he began his speech, shows two security teams walking on the roofs of two warehouses behind the stage.
Trump begins speech
At 6.05pm local time Trump began his speech on stage to crowd chants of “USA”.
As Trump speaks, the two security teams are seen on top of the warehouses. Security experts have told Sky News that it’s highly likely more than two sniper units were present.
In a video taken by a member of the crowd, one security member is seen looking through binoculars facing west (labelled two in the map above).
Neither of the two officers seen in footage appear to be holding guns, with one facing away from the rally and the other towards the former president – but not in the direct direction of the gunman.
One security expert said there would have been several countersniper teams at the event and not all of them would be holding firearms at all times.
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Tim McMillan, who worked on several presidential and vice-presidential security details and is a retired law enforcement professional said for countersniper teams “it isn’t just all about having your gun at the ready, it also relates to scouting external threats, really far out perimeter threats”.
In another video filmed from the crowd, as Trump continues to talk, the other security team on the roof of the other warehouse can be seen (labelled one in the map above).
Both are armed with weapons pointing north in the general direction of where the gunman is positioned.
Sky News analysis of the area suggests a large tree blocked the view between the gunman and this unit. This means only the pair of snipers furthest from the attacker had a clear view of him.
However, in the days before the event, the rooftop from which the gunman fired was identified by the Secret Service as a potential vulnerability, two sources familiar with the agency’s operations have told NBC News.
Another video filmed at the rally moments before the attack shows three police cars next to the building on to which the gunman had climbed – with the closest we found just 20m/65ft away.
Crowd spot gunman on roof
Around four minutes into his speech, a crowd member spots the gunman on the roof of the building.
“Yeah, someone is on top of the roof”, a man is heard saying as he pans to the gunman – later identified by the FBI as 20-year-old Thomas Matthew Crooks. He is seen holding a rifle.
By cross-referencing a live stream of Trump’s full speech and matching the audio with the video taken by the crowd member – we found that the man who took the video appeared to have spotted the gunman four minutes after Trump began speaking.
Other crowd members may have spotted the gunman before this video was taken.
Unaware of the gunman, Trump turned to the topic of immigration.
Local officer reportedly saw gunman
The Associated Press (AP) reports that several crowd members had told local officers Crooks was acting suspiciously and pacing near metal detectors, according to a law enforcement official who spoke on the condition of anonymity.
Officers were then told Crooks was climbing a ladder, the official said, adding that officers searched for him but were unable to find him before he made it on to the roof.
Butler County Sheriff Michael Slupe told AP that a local officer did climb up to the roof and encountered Crooks, who saw the officer and turned towards him, forcing the officer to drop down to safety.
Mr Slupe said the officer couldn’t have wielded his own gun under the circumstances. The officer retreated down the ladder and soon afterwards Crooks began shooting, according to two officials who spoke to AP anonymously.
Shots fired at Trump
In the seconds before the first shots are fired, both sniper units seem to get into position. The gunman then fires three initial gunshots, another five follow in quick succession three seconds later.
As the first shot rings out, Trump raises his hand to his right ear and looks at it, before quickly crouching to the ground.
Audio analysis by Sky News indicates that there is a six-second gap between the gunman’s first shot and the first shot taken by the Secret Service.
One final shot by a law enforcement sniper is heard 10 seconds later.
Secret Service agents rush to the stage and pile on top the former president to shield him as the gunman is shot dead by the snipers.
Sky News analysis found that the gunman began shooting two minutes after he was spotted by the man filming the videos we analysed.
Shortly after Trump, having been hit in the ear, gets to his feet and lifts his right fist before he is scrambled into a vehicle and taken to hospital.
Why was gunman within 150 yards with rifle?
A security expert told Sky News the US Secret Service is “ultimately responsible” adding that the gunman should not have been able to get within 150 yards (137 m) of the former president.
Former senior executive from FBI counterterrorism and senior vice president for global operations for the Supine Group, Christopher O’Leary, said: “The Secret Service was responsible for protecting former President Trump and the crowd that was there as well. They have concentric circles of protection that go out and theirs ended at the fence line.
“But they have state and local law enforcement that were responsible for those other perimeters. They should have had other Secret Service personnel coding, coordinating that out there and clearly they didn’t.
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“The real question is, why was this individual within 150 yards with a high-powered rifle?”
Mr O’Leary added that the Secret Service were presented with a “really challenging mission” due to factors including the “open-air space” venue chosen by Trump and his campaign, which makes it more difficult to protect.
Additional reporting by Megan Baynes, digital investigations reporter and Michelle Inez Simon, visual investigations producer.