WATCH: Vester Lee Flanagan chased driver who told him to slow down in July road-rage incident

The ex-journalist who shot and killed two reporters in cold blood on Wednesday was caught on tape last month having a road rage meltdown at another driver.

According to the New York Daily News, Vester Lee Flanagan II -- whose on-air name at WDBJ was Bryce Williams -- was recorded in a confrontation with Brandon Foster on July 6 in Roanoke, Virginia.

"He was obviously not in the right mind," said Foster to CNN. "He was driving in excess of 100 mph."

The two men were driving on a wet day when Foster noticed Flanagan driving aggressively and well over the speed limit in a silver Ford Mustang.

At a traffic light, Foster pulled up next to Flanagan and said, "You're driving like a lunatic."

"He rolled his window down further and said 'what'd you say?' I said, 'you're driving like an a--hole in the rain. You're endangering people’s lives on the road, you a--hole.'"

Flanagan then began to angrily pursue Foster through traffic, leading to the confrontation in the video below.

The two men exchanged angry words while simultaneously filming each other with their cell phones.

"You call a guy out for driving like a prick and you think he's going to lose his mind," Foster muttered as he walked away from the man who went on to gun down two colleagues and then fatally shoot himself.

Flanagan was a perennially disgruntled employee who launched a number of lawsuits against former employers alleging racial and antigay bias. He was fired from WDBJ last year and the lengthy manifesto he faxed to ABC News the night before the murders indicates that he had been planning the attack for some time.

“Why did I do it? I put down a deposit for a gun on 6/19/15. The Church shooting in Charleston happened on 6/17/15,” Flanagan wrote. “What sent me over the top was the church shooting. And my hollow point bullets have the victims’ initials on them.”

He idolized Virginia Tech shooter Seung-Hui Cho and other mass killers.

“The church shooting was the tipping point," he said, "but my anger has been building steadily...I’ve been a human powder keg for a while...just waiting to go BOOM!!!!”

Watch video about this story, embedded below: