MONETA, Va. - Vester Flanagan had become increasingly volatile in recent years, picking fights with co-workers and strangers over seemingly mundane incidents or perceived slights well before he fatally shot two former colleagues on live television.

Flanagan offered a variety of motives before he killed himself Wednesday: A rambling 23-page manifesto sent to a national news network described his ambush as revenge for the killings of nine black people inside a church in South Carolina, which prompted federal hate crime charges against a white suspect. On social media, Flanagan claimed his victims, 24-year-old Alison Parker and 27-year-old Adam Ward, had wronged him.

WDBJ-TV's general manager, Jeffrey Marks, flatly denied that his employees did anything wrong, noting that Flanagan had been fired because of many performance and behavioral problems. Marks said he alone was probably responsible for any workplace conflicts.

The ambush appeared to be carefully planned; Flanagan had contacted ABC News weeks ago with what he claimed was a story tip, had rented what he ultimately used as a getaway car and was carrying possible disguises: extra license plates, a wig, shawl, sunglasses and a hat. After the killing, he texted a friend suggesting he had "done something stupid," investigators wrote in a search warrant.

Flanagan's grudge against the local station dated to 2013, when he sued WDBJ a month after he was fired, claiming racial discrimination.

Court documents show he was fired for what managers called poor performance and an unending stream of conflicts with co-workers. It began within two months of his start at WDBJ, when he was written up for inappropriate behavior.

News director Dan Dennison wrote that Flanagan made co-workers feel threatened or uncomfortable. In one case, he lost his temper in a live truck. In another, photographers said he complained about shaky video without having seen it.

When he was finally fired in February 2013, company memos say he refused to leave and the station called 911 to have two police officers escort him out of the building. A human resources representative, Monica Taylor, reported in a memo that Flanagan said, "I'm not leaving. I'm going to make a stink and it's going to be in the headlines."

As Flanagan was being escorted out, he put a wooden cross in Dennison's hand, saying "You'll need this," according to Dennison.

Ward documented this altercation with his camera, prompting more insults from Flanagan, according to the court records.

Flanagan's lawsuit claims the station's camera operators conspired against him because of his race. It says a watermelon at the station was a racial slur, directed at him.

He asked for a trial by a jury comprised entirely of black women. A judge dismissed the case in July 2014, week before the trial date.

Marks said Flanagan raised no red flags when he was hired, getting positive references and passing background checks. But things went awry when his performance failed to improve, and he failed to check his facts, Marks said. Flanagan was fired after he confronted an anchor who was assigned to review one of his stories.

Flanagan remained in Roanoke after that, finding work at a health insurer's call center.

"We are still at a loss to know what happened to him in these 2-and-a-half years," Marks said Thursday at a news conference where station staff wore ribbons representing their slain colleagues.

Other WDBJ employees occasionally saw him around town without any confrontations. But Flanagan had other run-ins after his time at the station.

Heather Fay, general manager at a Jack Brown's beer and burger restaurant, said she received a 15- to 20-page letter from Flanagan three or four months ago criticizing the staff for telling customers to "have a nice day" instead of "thank you."

"You could tell he was really angry," Fay said. "It was bizarre, for sure."

Fay said she threw the letter out shortly after receiving it, but wrote down his name and a general description of his letter in her manager's notebook just in case. There was nothing in the letter suggesting that the author was contemplating a crime, she said. "I thought the guy had a lot of time on his hands," Fay said.

Flanagan did frighten another former co-worker, at the UnitedHealthcare call center in Roanoke.

Michelle Kibodeaux, 46, described him as loud and boisterous, with a booming laugh. He often remarked on how quiet she was, she said.

"One day he was being quiet, and I told him, 'You're being quiet today. The shoe's on the other foot.' He said, 'You don't know me well enough to judge me.'"

Kibodeaux said she turned to walk away and Flanagan tried to grab her by the shoulder, but she ducked under his hand.

"He said, 'Don't you walk away from me. Don't you turn your back on me,'" she recalled.

"I said, 'This is not going to happen.' And he said, 'Don't you ever speak to me again," Kibodeaux said.

Kibodeaux said she reported the encounter to a company official who said she was overreacting, and suggested giving him space.

"After that, I tried to steer clear. I only talked to him if I had to," she said.

UnitedHealthcare spokesman Matt Burns confirmed in email Wednesday that Flanagan worked as a call center representative at the Roanoke facility from September 2013 until November 2014. He declined to say if Flanagan had any problems, or whether he was fired or quit on his own.