The former TV reporter who shot two journalists dead during a live broadcast in Virginia before killing himself warned he had been a "human powder keg... just waiting to go BOOM."
The gunman -- Vester Lee Flanagan, 41, also known as Bryce Williams -- posted chilling footage of Wednesday's murder online.
Reporter Alison Parker, 24, and cameraman Adam Ward, 27, were fatally shot at close range while conducting an on-air interview for WDBJ, a CBS television affiliate in Roanoke, about 240 miles (385 kilometers) southwest of Washington.
It was unclear whether the shooter even knew Parker before the attack.
Friends, family and the community at large mourned the tragedy, as the incident renewed calls for gun control. Flanagan was said to have bought his gun legally.
The killings once again highlighted gun violence in America -- prompting a quick White House call for action -- and also raised questions about how the Internet provided a brief but unfiltered window on a horrific crime.
"It breaks my heart every time you read or hear about these kinds of incidents," President Barack Obama told an ABC affiliate in Philadelphia.
TV video frame grab courtesy of WDBJ7-TV station in Roanoke, Virginia shows Alison Parker (L) during an interview with local chamber of commerce director Vicki Gardner at a water park just before she was shot and killed.
The disturbing video of the deadly on-air shooting -- apparently filmed by Flanagan himself -- was posted on Twitter and Facebook. The footage was later removed.
"You send people into war zones and into dangerous situations, into riots, and you worry that they're going to get hurt," WDBJ general manager Jeffrey Marks told CNN.
"You send somebody out to do a story on tourism, and this -- how can you ever expect something like this to happen?"
Shots and screams
Parker was interviewing Vicki Gardner, head of the Smith Mountain Lake Chamber of Commerce, at the lakeside Bridgewater Resort in the town of Moneta near Roanoke when the attack occurred.
Several shots were heard, as well as screams, as Ward's camera fell to the floor, capturing a fuzzy and chilling glimpse of the gunman pointing his weapon at the ground.
The station then hastily cut away to a startled anchorwoman back in the studio.
Later, a video apparently posted by Flanagan under the Twitter account @bryce_williams7, showed the shooter brandishing a weapon at Parker.
Both she and Ward apparently did not see the shooter.
Undated photo courtesy of WDBJ7-TV in Roanoke, Virginia shows Alison Parker and Adam Ward, two WDBJ7-TV employees, who were killed in an attack at Bridgewater Plaza in Moneta, Virginia on August 26, 2015.
Multiple shots and screams are then heard, and Parker runs away.
The shooter's hand is clearly visible. He appears to be wearing a blue checkered shirt.
Gardner, 62, was in stable condition at a Roanoke hospital.
ABC News said it received a 23-page manifesto from a man identifying himself as Bryce Williams nearly two hours after the shooting.
A man later called the network and said he had shot two people. He said authorities were "after me" and "all over the place" before hanging up, according to ABC.
In the rambling manifesto, Flanagan -- an African American sacked in 2013 by WDBJ -- said he was sent over the edge by the June mass shooting of black worshippers at a church in South Carolina.
Describing himself as a "human powder keg... just waiting to go BOOM!!!!," Flanagan also complained in what he called a "Suicide Note for Friends and Family" of racial discrimination and bullying "for being a gay, black man."
"Yes, it will sound like I am angry... I am. And I have every right to be. But when I leave this Earth, the only emotion I want to feel is peace," it said.
Marks, the station manager, said Flanagan was dismissed "after many incidents of his anger coming to the fore."
Parker's boyfriend, WDBJ anchor Chris Hurst, said on Twitter that he was "numb," saying the pair were "very much in love" and had just moved in together.
"We were together almost nine months. It was the best nine months of our lives. We wanted to get married," he said.
Virginia residents pay their respects at a makeshift memorial for reporter Alison Parker, 24, and cameraman Adam Ward, 27, at the gate of WDBJ television studios on August 26, 2015, in Roanoke, Virginia.
The cameraman's fiancee, Melissa Ott, a producer at the TV station, watched the shooting play out on air from the control room.
Ott was working her last day at WDBJ before moving on to another station in another city, and looking forward to a farewell party with her colleagues.
"This was going to be a day of celebration for her time here and wishing her good luck," Marks told CNN, adding staff were very emotional and planning a memorial gathering.
The shooting, which took place not far from the scene of the Virginia Tech University mass killing in April 2007, launched a fresh round of hand-wringing about gun control in America.
The reporter's father, Andy Parker, made a plea for action after the murder of his daughter, who he described as "our bright, shining light."
"We've got to do something about crazy people getting guns," he told Fox News.
"What we know is that the number of people who die from gun-related incidents around this country dwarfs any deaths that happen through terrorism," said Obama, who has talked openly about his frustration at not making headway in gun-control laws.
Even in the face of mass shootings, US lawmakers have been hesitant to enact tougher limitation on access to guns, in part because they are loath to anger constituents who fiercely defend their constitutional right to bear arms.
Democratic presidential candidate Hillary Clinton said she was "heartbroken and angry."
"We have got to do something about gun violence in America," she said on the campaign trail.