The suspected shooter, Sam Cassidy, killed himself after killing nine others who worked with him at the station.
We spoke to an ex-girlfriend of Cassidy.
The woman does not want to be identified. She had a court case against Cassidy in 2009, claiming that he threatened her and sexually assaulted her.
She repeatedly mentioned that he was "not mentally stable."
She says he suffered from mood swings and had issues with his coworkers, that he was "always complaining about his job." It was "it was too much work, stressful, his boss was mean to him," she said.
"They treat him bad," she explained, but kept reiterating that he had a "mental problem," and was "mentally up and down."
The woman said, "I was lucky he didn't kill me," explaining that they had "issues," and when he proposed to her, she turned him down.
"You know one day he is a nice guy, a gentleman, tells me how much he loves me and cares about me. Then after, he's totally different."
Cassidy's motive is still under investigation.