A doctor announced Tuesday that former NFL cornerback Phillip Adams suffered from chronic traumatic encephalopathy (CTE) when he killed six people and himself in April.

According to Josh Peter of USA Today, Boston University CTE Center Director and neuropathologist Ann McKee made the determination after examining Adams' brain.

McKee called Adams' case of CTE "severe" and noted it was comparable to former New England Patriots tight end Aaron Hernandez, who was convicted of the murder of semi-pro football player Odin Lloyd in 2015 before killing himself in 2017.

On April 7, Adams shot and killed Dr. Robert Lesslie at his home in Rock Hill, South Carolina. Adams also shot and killed Lesslie's wife Barbara, Lesslie's grandchildren Adah and Noah, and air conditioning repairmen James Lewis and Robert Shook.

Adams fled the scene and later shot and killed himself at the age of 32.

Per Peter, Adams' sister Lauren said he showed signs of distress leading up to the killings:

"His mental health degraded fast and terribly bad. 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."

CTE is a degenerative brain disease that has been found in the brains of many former NFL players as a result of head trauma experienced throughout their careers.

Adams played collegiately at South Carolina State before the San Francisco 49ers selected him in the seventh round of the 2010 NFL draft.

He went on to spend six seasons in the NFL, playing for the Niners, New England Patriots, Seattle Seahawks, Oakland Raiders, New York Jets and Atlanta Falcons.