The sister of the shooter in the Rock Hill, South Carolina killing is speaking out, saying her brother “wasn’t a monster.”

“His mental health degraded fast and terribly bad,’’ Lauren Adams told USA TODAY Sports. “There was unusual behavior. I’m not going to get into all that [symptoms]. We definitely did notice signs of mental illness that was extremely concerning, that was not like we had ever seen. …

“He wasn’t a monster. He was struggling with his mental health.”

Phillip Adams, 32, who played for the San Francisco 49ers and New England Patriots, shot two air conditioning technicians, Dr. Robert Lesslie, his wife, Barbara Lesslie, and two grandchildren, ages 5 and 9, on Wednesday.

The mass shooting left authorities baffled. Phillip Adams was later found dead in his parents’ house. He had a self-inflicted gunshot wound.

During his time playing football, from 2010 to 2015, Adams suffered two concussions, but there is no evidence to support that he had long-term brain trauma from the incidents. However, Lauren says that “there was unusual behavior.” According to her statement, there were “signs of mental illness that was extremely concerning, that was not like we had ever seen.”

Adams’ family is shocked by his actions. But his sister and father, Alonzo Adams, told news outlets that “he’s a good kid – he was a good kid.” They say the former NFL player suffered from horrible mental health issues prior to the tragedy.

His father believes he was “messed up” by football. His sister claims that her brother didn’t leave the sport with a good feeling about the game. If the family was watching a game in the living room he would ask them to turn it off. Lauren noticed that “in conversations, it would escalate to arguments … He was super laidback forever and, all of the sudden, he had that temper. You could just tell that something was off.”

The family says the situation deteriorated in the last 18 months. “We wouldn’t hear from him for months. It was totally unlike him. He has always been a family person.”

He reportedly began to neglect his hygiene and withdrew from people. Then, at a funeral two weeks before the shooting, Phillip told his sister that he applied for disability benefits with the NFL, but that the NFL was making it hard for him.

“Towards the end,” she told USA Today, “he felt like they were trying to basically stiff him out on money … I think he got upset about that and that’s kind of where it all started.”

In Rock Hill, South Carolina, Adams was previously considered a role model. He even mentored children. NFL agent Scott Casterline told the Charlotte Observer that “the Phillip that [he] knew was a really good person, quiet. He’s a loner, but he was good, he was a good person.”