An attendee at former President Trump’s rally in Pennsylvania claimed that he and others warned authorities about a man he said was armed with a rifle and climbing up a roof just moments before opening fire, in an apparent assassination attempt Saturday evening.

The witness, who was standing with others just outside the event in Butler, told BBC News that he had seen the shooter crawling onto a nearby roof shortly after Trump started speaking at the rally.

"We noticed a guy crawling, army – bear crawling up the roof of the building beside us, 50 feet away from us," he said. "We’re standing there, we’re pointing at the guy crawling up the roof."

He told the BBC that he could "clearly see him with a rifle," though he could not tell what type due to the distance. He described the gunman as wearing muted, tan-type clothing.

LIVE UPDATES: FORMER PRESIDENT TRUMP SURVIVES ASSASSINATION ATTEMPT, FBI IDs SHOOTER AS THOMAS MATTHEW CROOKS

Trump holds fist

Former President Trump is seen with blood on his face surrounded by Secret Service agents as he is taken off the stage at a campaign event at Butler Farm Show Inc. in Butler, Pennsylvania, on Saturday. (Rebecca Droke/AFP via Getty Images)

The witness detailed how he and others tried to warn police and the Secret Service.

"We’re pointing at him," he said. "The police are down there running around on the ground. We’re like, ‘Hey man, there’s a guy on the roof with a rifle.’ And the police were like, ‘Huh, what,' you know, like they didn’t know what was going on."

Donald Trump reacts as multiple shots rang out during a campaign rally

Former President Trump grabs his right ear as multiple shots rang out during a campaign rally at the Butler Farm Show in Butler, Pennsylvania, on Saturday. (Reuters/Brendan McDermid)

The witness said that they continued to point out the gunman, saying they could still see him crawling on the roof.

Republican presidential candidate and former U.S. President Donald Trump is assisted by guards during a campaign rally

Former President Trump was helped up to his feet by U.S. Secret Service agents during a campaign rally at the Butler Farm Show in Butler, Pennsylvania, on Saturday. (REUTERS/Brendan McDermid)

"I’m standing there pointing at [the gunman] for two to three minutes," he said. "Secret Service is looking at us from the top of the barn. I’m pointing at that roof … and next thing you know five shots ring out."

BIDEN SPOKE WITH TRUMP FOLLOWING SHOOTING AT PENNSYLVANIA RALLY

He said that Secret Service agents who were on top of a nearby barn were looking in their direction with binoculars, but likely could not see the gunman due to the way that the roof he was on sloped, obscuring the shooter’s body.

Donald Trump is surrounded by U.S. Secret Service agents at a campaign rally

U.S. Secret Service agents surround former President Trump is surrounded after a gunman fired shots at a campaign rally on Saturday in Butler, Pennsylvania. (AP Photo/Evan Vucci)

After the initial shots were fired, the witness detailed seeing the Secret Service respond.

"They blew [the gunman’s] head off," he said. "Secret Service blew his head off."

Armed men stand over a downed suspect, whose face is blurred

Authorities approach the suspected gunman from where he fell after the U.S. Secret Service returned fire after an apparent assassination attempt on former President Trump. (Obtained by Fox News Digital)

He went on to question why Trump had not been pulled off the stage after they had pointed out the gunman, and why the Secret Service had not been present on every roof in the nearby area.

Trump, who appeared bloodied as the Secret Service rushed him off the stage and into a waiting SUV, later posted a statement on Truth Social, saying that he "immediately felt the bullet ripping through the skin." 

The FBI has identified Thomas Matthew Crooks, 20, of Bethel Park, Pennsylvania, as the shooter. Bethel Park is a Pittsburgh suburb about an hour south of where the assassination attempt took place.

CLICK TO GET THE FOX NEWS APP

At least one rally attendee was killed, and two spectators were critically injured, authorities said. All were identified as men.