Police are searching the Northwest for a man accused of killing his Seattle-area grandparents, who had just picked him up after his release from a Washington state prison, hosted a party in his honor and offered him a room in their home for the night.

Police say 26-year-old Michael "Chad" Boysen is considered extremely dangerous and has tried to obtain guns.

Boysen was released from prison Friday after serving several years for robbery. King County Sheriff John Urquhart says Boysen's grandparents - an 82-year-old man and 80-year-old woman - picked him up from prison and hosted a family "welcome home party" for him that night.

The couple was killed later Friday or early Saturday at their Renton home. Authorities believe Boysen also stole their car.

A warrant was issued for his arrest.