A TV news reporter and cameraman who were murdered this week both received gunshot wounds to the head, Virginia medical officials have said. The manner of deaths for Alison Parker, 24, and Adam Ward, 27, who both worked for CBS affiliate WDBJ7, have been classed as homicide.

The pair were shot by a former co-worker – 41-year-old Vester Lee Flanagan, aka Bryce Williams – while Parker was conducting a live interview. Parker was shot in the head and chest, while Ward received shots to the head and torso. It is not clear how many times they were shot.

Both Parker and Ward died at the scene, while the interviewee – Vicki Gardner, the executive director of the Smith Mountain Lake Regional Chamber of Commerce – was shot in the back. She came out of surgery on Thursday 27 August in stable condition after reportedly losing a kidney and part of her colon.

Following the murder of his former co-workers, Flanagan posted a 56-second video of the violence against them on Twitter and Facebook. The footage was removed. Two hours after he shot Parker and Ward at 6:45am, Flanagan sent a 23-page fax to ABC's newsroom under his professional name. He complained that he had been the victim of discrimination and was bullied at work for being gay and black. He said that his annoyance had been "building steadily" and that he had turned into a "human powder keg" that was "waiting to go BOOM!!!!" After a police chase, Flanagan shot himself and later died in hospital.

Parker's father has said that he would become a crusader for gun control. "Nationally, locally, you've got to find a way to keep crazy people from getting guns," Andy Parker said. "And I'm relentless and I'm not going to stop until something happens because I don't want to see another tragedy like this again."

He also said that the powerful US gun lobby group, the National Rifle Association, would argue that his daughter and her colleague would have been safe had they too been armed. There have been 247 mass shooting incidents in the US so far in 2015.