Serious questions are being raised about the response times by security personnel at former President Trump’s Pennsylvania rally Saturday after several witnesses say they warned authorities about the shooter moments before he opened fire – and that security in general at the event was "lax."

Trump says a bullet pierced the upper part of his right ear while officials say three spectators were hit by gunfire – one of whom was fatally struck. 

Eyewitness Greg Smith told BBC News that he and others saw the man "bear crawling" on the roof of a nearby building just outside the event in Butler, shortly after Trump had begun speaking. 

Smith said he tried to alert the authorities for three to four minutes, but thought they probably could not see the gunman because of the slope of the roof.

SHOOTING AT TRUMP RALLY BEING INVESTIGATED AS ASSASSINATION ATTEMPT

"We noticed a guy crawling, army – bear crawling up the roof of the building beside us, 50 feet away from us," said Smith, who was standing with others just outside the event in Butler. "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," and that 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."

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

The seemingly delayed response has called into question if the law enforcement or the Secret Service could have reacted more quickly in engaging the shooter, later identified as 20-year-old Thomas Matthew Crooks.

Video from the rally posted to social media shows others spotted the gunman too, moments before the shots rang out. People could be heard yelling, "He's got a gun!"

One person says, "Shoot him," referring to the gunman, and another can then be heard yelling, "He’s on the roof" before shots ring out.

Meanwhile, another eyewitness, Benjamin Shrader, told Fox News Digital that security at the rally was "terrible." 

BIDEN SPOKE WITH TRUMP FOLLOWING SHOOTING AT PENNSYLVANIA RALLY

"I had to give all my information and security in the special guest section and that was great," he said. "But overall for the event, the security was extremely lax.". 

Shrader added that the screening for general admission before the event was lacking.

"There were only metal detectors and then a pat down. That was it," he said. "There was nobody going around the fences and somebody could have easily thrown a gun in."

The U.S. Secret Service (USSS) later said, in a news release, that the suspected shooter fired from an "elevated position," killing at least one person and critically injuring two others.

Shrader said the security at the special guest section was "great," but overall security at the major political rally was "lax."

"I had to give all my information and security in the special guest section and that was great," he said. "But overall for the event, the security was extremely lax."

Shrader added that the screening for general admission before the event was lacking.

"There were only metal detectors and then a pat down. That was it," he said. "There was nobody going around the fences and somebody could have easily thrown a gun in."

The U.S. Secret Service (USSS) later said, in a news release, that the suspected shooter fired from an "elevated position," killing at least one person and critically injuring two others.

Former FBI special agent and Navy SEAL Jonathan Gilliam told "Fox & Friends First" that the response times of Secret Service agents on the ground was terrible.

"I could not believe how long it took them to get him off of that stage, into the car, and then it took that vehicle that long to depart that area. It was a lifetime from a protection standpoint," Gilliam said.

"A lot of people on the news… didn’t want to be critical of the Secret Service but as I watched this again… I’m astounded at the way things played out because it appeared that the defense of Trump and the movement off were being made up as they went along and that is not the way this elite service should be prepared for this and carrying out these tactics in this type of situation," Gilliam continued. "The one person that reacted properly was Donald J. Trump when he hit the ground and got as low as he could. From a protective standpoint, it took forever for [the Secret Service] to get on him and longer for them to react and get him out."

"I can’t believe what I’m seeing, these Secret Service agents don’t know whether to holster their gun or keep it out, keep their sunglasses on or take [them] off," he added. "He should have been out of there so fast that the people didn’t even realize that he had gone yet."

However, former Secret Service special ops ace Marshall Mirarchi said on "Fox & Friends Sunday" morning that the Secret Service personnel on the ground during the assassination attempt "did an amazing job" and that they were likely told to hold Trump on the stage.

"I think they did a great job with what they had from doing these events for over 10 years. It is very frustrating, [I’m] surprised this doesn’t happen more often, you don’t always have the resources available or the personnel. That’s why you have questions about the perimeter and how someone was able to get so close to it."

Some experts, like Gilliam, have suggested the Secret Service should have gotten Trump off the stage earlier, but Mirarchi says they likely got a call to hold him at the podium in case there was another shooter – and if they stood him up sooner it could have potentially opened him up to being struck again.

"They all dive right on the president, I think they executed that as perfectly as can be, then right after that you see the counter-assault team take the stage… with the gear and the rifles, the helmets, that group, you can see them as well and in the other videos[and] you have your counter-sniper teams on the roof who took out the shooter."

"We all train together… we go over these scenarios thousands and thousands of times. The only Monday morning quarterback thing is there just needs to be more people and that comes down to personnel, to the budget… but they need more resources."

Mirarchi says agents work up to 60 days in a row, 12 to 14 hours per day, going from event to event.

"A lot of people are quick to rush to judgment, but I do want to highlight… that the men and women on the ground there… I think they did a great job with the resources that they had."

Fox News' Stephen Sorace, Chris Pandolfo, Sarah Rumpf-Whitten and Matteo Cina contributed to this report.