Internal memos from Dan Dennison, then news chief of WDBJ7, show concerns about Vester Flanagan’s “aggressive” behaviour towards colleagues.
They indicate the station tried to help him before firing him in February 2013.
Flanagan shot dead Alison Parker and Adam Ward at a shopping centre in Moneta on Wednesday.
He filmed the attack and posted it on social media. ABC News also said it had received a rambling fax from the 41-year-old describing himself as a “human powder keg”.
The White House said Wednesday’s attack showed the need for better gun control.
Flanagan was hired by WDBJ7, in Roanoke, Virginia, in March 2012 and was known on air by his professional name, Bryce Williams.
Within a few weeks, colleagues were complaining of “feeling threatened or uncomfortable” while working with him.
The memos highlight “heated confrontations” with camera operators and producers in front of guests while out covering stories.
By July 2012, Mr Dennison was requiring him to contact the Health Advocate, the employee assistance programme, or face being sacked.
“We can no longer afford to have you engage in behaviours that constitute creation of a hostile work environment,” he said.
- Aged 24, was a reporter for WDBJ7’s Mornin’ show
- Grew up in Martinsville, Virginia and edited her university newspaper
- Joined WDBJ7 after internship and said she grew up watching the station
- Was dating station anchor Chris Hurst
- Aged 27, was a cameraman for WDBJ7
- Went to school in Salem, Virginia, and graduated from Virginia Tech
- Described by his employer as committed and a “fine photojournalist”
- Was engaged to station producer Melissa Ott
Speaking on Wednesday from Hawaii where he now works, Mr Dennison said Flanagan had complained of racial discrimination but “all these allegations were deemed to be unfounded”.He said when Flanagan was fired, he had to be escorted from the building by police “because he was not going to leave willingly or under his own free will”.
In the 23-page fax to ABC News apparently sent by Flanagan under his professional name, he complained of suffering discrimination and bullying at work for being gay and black.
He said his anger had been “building steadily” and that he had become a “human powder keg” that was “waiting to go BOOM!!!!”
The writer expressed admiration for the teenagers who killed 13 people at Columbine High School in Colorado in 1999 and said the attack in Charleston, South Carolina, in which nine black churchgoers were killed in June this year, was what “sent me over the top”.
Late on Wednesday, a representative for Flanagan’s family issued a statement expressing their “deepest condolences to the families of Alison Parker and Adam Ward”.
“Our thoughts and prayers at this time are with the victim’s families and with WDBJ television station family,” the statement added.
Reporter Alison Parker and cameraman Adam Ward were conducting a live interview with a guest on tourism for the breakfast show early on Wednesday when the incident occurred.
Suddenly, shots rang out, and viewers saw the camera fall to the ground. Screams could be heard and the footage captured a brief glimpse of the gunman.
The station cut back to the studio – journalists would later have to continue broadcasting on the deaths of two of their colleagues.
Hours later, the gunman posted footage online of himself opening fire at close range. This was later removed.
He killed himself after a police chase.
The interviewee, Vicki Gardner of the Smith Mountain Lake Regional Chamber of Commerce, is in a stable condition in hospital following surgery.