After he shot two journalists on live TV and before he shot himself, Bryce Williams sent a message: "I've been a human powder keg for a while....just waiting to go BOOM."

 

Those were the words the gunman wrote in a chilling fax to ABC News, according to the network. The document purportedly from the Virginia shooter came after he gunned down WDBJ-TV journalists Alison Parker and Adam Ward, spurring a manhunt that ended when he turned a gun on himself as troopers closed in.

 

The shooter -- a former reporter for the Roanoke station -- is dead, but the investigation into Wednesday's attack is far from over. Authorities say the fax to ABC, the gunman's other attempts to reach out to the media and his social media posts just after opening fire could be key pieces of evidence as they try to pinpoint what led to the deadly shooting.

 

Franklin County Sheriff Bill Overton said authorities weren't sure about the gunman's motive, but are looking at his past employment at WDBJ as well other evidence, including the fax he allegedly sent to ABC News in New York.

 

"Many of you have gotten a lot of the correspondence, emails that had been sent out. It's obvious that ... this gentleman was disturbed in some way of the way things had transpired," and that "at some point in his life, things spiraled out of control," Overton said.

 

According to ABC, a 23-page fax to the network arrived almost two hours after the shooting. It came from someone who identified himself as Bryce Williams, the on-air name gunman Vester L. Flanagan II used when he worked as a reporter.

 

In the message, according to ABC, the gunman said the Charleston, South Carolina, church shooting in June is what put him over the edge, but he wrote that his "anger has been building steadily" because of racial discrimination and sexual harassment he claims to have endured.

 

The writer expressed admiration for the shooters who massacred students at Columbine High School and Virginia Tech. And he said he put a deposit down for a gun two days after the Charleston shooting.

 

"As for Dylann Roof? You (deleted)! You want a race war (deleted)? BRING IT THEN YOU WHITE (deleted)!!!" the document reportedly said.

(CNN)