DURHAM, N.C. -- Durham police are still trying to figure out if a man died of natural causes or was murdered.

• William Bishop died in April.
• Warrant: Bishop was strangled.
• Bishop found with a dog leash around his neck.          

William Bishop died last month and family and friends said he suffered a heart attack.

However, a newly-released search warrant says the 59 year old was strangled.

The warrant says Bishop’s son found his dad with a leash wrapped around his neck and the dog on the other end.

The son also told authorities his father was abusive and said he was not upset that he was dead.

Police have not named a suspect and say the investigation continues.

Police searched Bishop's home and they took the son's cell phone.