The doctor who discovered chronic traumatic encephalopathy, the brain disease better known as CTE, is convinced that the condition is what drove former New England Patriots tight end Aaron Hernandez to take his own life.

Hernandez’s fiancee Shayanna Jenkins filed a lawsuit against the Patriots and the NFL on Thursday, claiming the former tight end had a severe form of CTE and the league and team did nothing to protect him from it. Dr. Bennet Omalu, the man who discovered CTE and inspired the film “Concussion,” told TMZ on Friday that he has no doubt the brain disease drove Hernandez to suicide.

“There is no question in my mind that CTE drove Aaron Hernandez to suicide and other criminal and violent behavior,” Omalu said. “If you read my book ‘Truth Doesn’t Have a Side’ you will encounter the Chapter titled ‘I bet my license OJ Simpson Has CTE,’ therefore, it should not be surprising that Aaron Hernandez eventually committed suicide.”