SEATAC, Wash. -

The King County sheriff's office says the death of a 100-year-old man whose body was found in his SeaTac, Washington, home is being investigated as a homicide.

Investigators say Robert O. Benson's wallet is missing and they are trying to locate it. The wallet contained credit cards and identification.

Sheriff's Sgt. DB Gates says a worried friend went to Benson's home to check on him last Friday morning and found the body. The cause of death has not been announced.

The Seattle Times reports that Gates says Benson had lived in his home for decades and was still driving and able to get around on his own.