(KRON) — Days after a 94-year-old Santa Rosa man was found dead “with no signs of trauma or foul play,” evidence revealed it was an “intentional killing,” the Sonoma County Sheriff’s Office said Saturday. The man’s son-in-law has been arrested on suspicion of murder.

The 94-year-old man, identified by authorities as Sy Van Nguyen, was reported to be unresponsive on Aug. 11 by his son-in-law, Khanh Trong Tran, 71, of Santa Rosa. First responders were dispatched to a residence on the 5800 block of River Road, where they pronounced Nguyen deceased.

“At that time, there were no signs of trauma or foul play, and his body was released to the family,” the sheriff’s office wrote.

On Friday, authorities said deputies received evidence that Nguyen’s death was not natural. An arrest warrant was obtained for Tran.

Tran was located on Saturday inside a vehicle in the 1700 block of Marlow Road and arrested for murder. He remains in custody without bail.