This story was originally published by the WND News Center.

A Pittsburgh television station is reporting “dramatic new details” in connection with the attempted assassination of former President Donald Trump on Saturday, with sources Monday saying law enforcement was made aware of gunman Thomas Crooks on the roof nearly half an hour before shots rang out.

WPXI-TV reports: “According to multiple law enforcement sources, Thomas Crooks was spotted by law enforcement on a roof nearly 30 minutes before shots were fired that injured Trump, killed a former fire chief, and injured two others in the crowd.”

Channel 11's Nicole Ford confirmed that Beaver County's ESU team had eight members at the rally, including snipers and spotters. According to Ford's sources, one of them noticed a suspicious man on a roof near the rally at 5:45 p.m., called it in and took a picture of the person. We have learned from our sources the person in that picture is Thomas Crooks. We're told it's not clear if Crooks had a gun with him at that point.

According to multiple sources, a law enforcement officer had also previously seen Crooks on the ground and called him in as a suspicious person with a picture prior to 5:45 p.m. Our sources tell us an officer checked the grounds for Crooks at that point, but did not see him where the first picture was taken.

26 minutes after the second picture of Crooks was taken by law enforcement and the information called in, shots were fired from the roof of the American Glass Research building. Seconds later, a Secret Service sniper returned fire and killed Crooks.

As WorldNetDaily previously reported, local police reportedly encountered Donald Trump’s would-be assassin Thomas Crooks just moments before he opened fire on the former president Saturday, but failed to stop the shooter despite the clear threat.

The New York Post reports: “After rallygoers spotted Crooks on the roof of a manufacturing plant just 130 yards from the stage where Trump was speaking just after 6 p.m. Tuesday, police were notified and one officer climbed a ladder to investigate, law enforcement officials said on the condition of anonymity.

"There the officer encountered Crooks, who pointed his AR-style rifle at them.

"The officer then backed down the ladder, and Crooks immediately took aim and loosed eight shots at the former president – grazing him in the ear, killing one bystander in the rally crowd, and gravely wounding two others.

"After that volley of shots, Secret Service snipers shot Crooks dead."

Meanwhile, another witness to the mayhem has been interviewed on camera, saying he saw the shooter "move from roof to roof" before shots were fired.

"I was up at the fence line, saw the guy [the attempted assassin] move from roof to roof. [I] told an officer he was on the roof," the man explained.

"I heard that there was somebody that could see the person, so I went back to where they were standing, saw the person, went back and told the officer again that if he goes back to that particular spot he can see the person, figuring that he would go and radio. An when I turned around to go back to where I was is when the gunshots started and then it was just chaos."

Earlier, another rally attendee told BBC News he tried to alert authorities to the gunman, to no avail.

"We're pointing at the guy crawling up the roof," the man explained.

"He had a rifle, we could clearly see him with a rifle absolutely. We're pointing at him. 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? 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 witness added he was "100%" certain the shots fired came from the gunman to whom he was trying to alert authorities.