The man accused of killing two broadcast journalists in Virginia was identified as Vester Lee Flanagan, a former employee at the station where the victims worked.
Police said Flanagan, 41, of Roanoke, Virginia, shot himself and later died after the murders on Wednesday.
Using the name Bryce Williams, Flanagan had worked as a TV journalist in several southern states for many years.
In March 2012, he was hired at WDBJ, the same Roanoke TV station where his victims Alison Parker and Adam Ward worked.
Jeffrey Marks, WDBJ's general manager, described Flanagan as unhappy, difficult to work with and always "looking out for people to say things he could take offence to".
"Eventually after many incidents of his anger coming to the fore, we dismissed him. He did not take that well,'' Marks explained. He said Flanagan had to be escorted by police out of the station when he was fired after less than a year in post.
Emails and letters sent to Flanagan by his bosses before he was fired told him to change his behaviour and also advised him to seek medical help.
"This is a mandatory referral requiring your compliance," one message from Dan Dennison, then WDBJ news director said.
"Failure to comply will result in termination of employment."
As police searched for Flanagan on Wednesday morning, more information surfaced.
He posted a video of the shooting to his Twitter account - an account which only had tweets two weeks old and included many childhood and other photos.
On Twitter, Flanagan also accused one of the murdered reporters of making racist comments and said the other victim complained to human resources about it.
ABC News said they had received a "lengthy" fax from someone purporting to be Bryce Williams between Tuesday night and Wednesday morning and had turned it over to the authorities.
The broadcaster described the 23-page letter as "rambling" and said the writer described being motivated by previous gunmen in US mass shootings - including those in Columbine and Virginia Tech, but said the "tipping point" was the murder of nine African-Americans in Charleston early this summer.
"I've been a human powder keg for a while… just waiting to go BOOM!!!!," he wrote.
He suggested on the Twitter account he had modelled as a child and young adult, been a "high paid companion", and was raised as a Jehovah's Witness.
Vester Lee Flanagan
2000 Hired as reporter but fired same year by WTWC-TV in Tallahassee, Florida. Case brought by Flanagan subsequently dismissed.
March 2012 Hired as a reporter at WDBJ-TV
30 July 2012 Told to improve behaviour or face the sack after complaints from other staff
February 2013 Sacked and escorted from WDBJ
May 2014 Sues WDBJ
July 2014 Judge dismisses case
According to his own LinkedIn account, he worked in several positions in customer service and had a degree in broadcast media from San Francisco State University.
He also worked for California's KPIX-TV in the early 1990s.
Local media reported Flanagan filed a lawsuit against WDBJ, alleging discrimination by the whole station, naming most of the staff in his complaint.
The case was dismissed by a judge in July 2014.
Flanagan also sued a Florida TV station in 2000 after he was fired - a case that was dismissed the next year. A local paper said he had also alleged racial discrimination.
Don Shafer hired Flanagan at WTWC and said he was a "good on-air performer, a pretty good reporter.
"And then things started getting a little strange," said Mr Shafer, now news director at San Diego News 6.
He was fired the same year for "odd behaviour."
However one woman who worked with him at a TV station in Savannah, Georgia, more than 15 years ago remembered him as a "good guy" who often joked with other staff, NBC reported.
Tarcia Bush, then also at WTOC-TV, said Flanagan "was such a mild-mannered guy.
"That guy that did this...is not the guy that I knew."