SANTA ROSA, Calif. - A Santa Rosa man has been arrested in the killing of his 94-year-old father-in-law, who authorities initially believed died of natural causes.

Suspect reported father in-law's death

What we know:

Khanh Trong Tran, 71, reported on Aug. 11 that his father-in-law, Sy Van Nguyen, was found unresponsive at a residence in the 5800 block of River Road, according to the Sonoma County Sheriff’s Office.

No initial signs of foul play

Dig deeper:

Nguyen was pronounced dead. At the time, there were no signs of trauma or foul play, and his body was released to the family, authorities said.

On Friday, deputies received evidence indicating the death was not natural but an intentional killing.

Violent crime investigators took over the case and obtained an arrest warrant for

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