The actor—who was best known for his role as zombie Mike in The Walking Dead—died in February at the age of 31. His body was discovered in his car in the Hudson Bridge area of Stockbridge, Georgia three days after he went missing.

An autopsy report, obtained by TMZ, found that a gunshot wound to the face was the cause of death, but investigators have been unable to determine the intent behind the shooting and whether a homicide or suicide took place.

Meanwhile, the actor’s family has expressed its belief that Moseley was kidnapped and murdered.

Moseley’s sister Teerea Kimbro told The Independent: “He’s never been in trouble with the law, ever in his life—so we knew that wasn’t it.”

Kimbro also questioned the suicide theory, asking how the gun ended up in his lap if he supposedly shot himself.

“He’s right-handed,” she said. “If you shoot yourself, the gun is going to end up falling on the right side of the car—not on your lap. So that doesn’t make sense either.”

Now Kimbro has said she received a letter from Joe Biden in relation to her brother’s death.

She shared a copy of the letter with TMZ, which published a photo of the correspondence.

Biden reportedly wrote: “Though the grieving process never quite ends, I promise you the day will come when the memory of Moses will bring a smile to your lips before it brings a tear to your eye.”

“My prayer for you is that this day comes sooner rather than later.”

Newsweek has contacted the White House for comment.

Police in Georgia had been investigating Moses’ death as a possible suicide but are not ruling out other scenarios.

“During the preliminary investigation, the potential of the death being a suicide was considered while not ruling out any other possibilities,” local police captain Randy Lee said last month per local outlet Times-Georgian.

“As investigators progressed their investigation and more evidence was processed, reviewed and analyzed, other possibilities have presented themselves, including accidental.”

Moseley had a recurring role in The Walking Dead between 2012 and 2015 as one of Michonne’s (Danai Gurira) pet zombies. His other acting roles included HBO’s Watchmen and the 2013 film The Hunger Games: Catching Fire.

If you have thoughts of suicide, confidential help is available for free at the National Suicide Prevention Lifeline. Call 1-800-273-8255. The line is available 24 hours every day.