The family along with their attorneys held a press conference in Beverly Hills on Tuesday announcing the filing.
Wilson Jr., who played for the Detroit Lions from 2005 to 2007, died on Feb. 1 while in custody at the Twin Towers Correctional Facility.
"We just want the truth," said Wilson Jr.'s father, Stanley Wilson Sr., who also played for the NFL. "It hurts really bad to bury your child."
The father described his son as a meek, humble, fun, loving, and charismatic man who attended Stanford University. The family said he suddenly became less social, more withdrawn, anxious and depressed.
They said Wilson Jr. suffered from chronic traumatic encephalopathy (CTE), a brain condition common among football players believed to be linked to repeated head injuries and blows to the head.
John Carpenter, the attorney representing the Wilson family, said that all led to an arrest for trespassing in August 2022.
"Due to his mental illness, the county found him not able to stand trial, not able to provide assistance to counsel, and so they put him in the [Twin Towers Correctional Facility] since august of 2022," he said.
In February, Wilson Jr.'s parents were notified of his death, but his parents continue to ask "Why?" and continue to wonder how he died.
The story has changed, ranging from his cell at the mental health facility to the ambulance to the hospital. Carpenter said marks on the former athlete's wrists and head tell a story of foul play.
"There were fresh wounds to his forehead, which appear to have been caused by a shoe," he said.
Wilson Jr.'s mother, who spoke at Tuesday's press conference in tears, remembered her last conversation with her only son, saying he was optimistic about his future.
"How he could change his life around and help somebody else," said Dr. Pulane Lucas.
A dream unfulfilled, leaving the grieving mother with a mission and message for other parents in search of answers about their child's death.
"I want you to know today I feel for you and I stand with you," she said.
Eyewitness News contacted the county for a statement regarding the claim and received the following statement:
"LA County offers its sincere condolences to Mr. Wilson's family. However, we cannot comment on this pending litigation at this time."