PORTLAND, Ore., March 12 (Reuters) - Police stormed a motel room in Oregon on Tuesday to end an eight-hour standoff and arrest an ex-convict accused of killing his grandparents after they had thrown him a party to celebrate his release from prison, authorities said.
The suspect, Michael "Chadd" Boysen, 26, was taken into custody by police in the coastal town of Lincoln City, 76 miles (122 km) southwest of Portland, at about 7 p.m. local time suffering from self-inflicted knife wounds, Police Chief Keith Kilian said.
Kilian did not say what prompted police to storm the motel room, blowing out windows with a water cannon and forcing the exterior door off its hinges before officers entered, but the chief said the suspect was easily subdued.
"He had injured himself, so he put up no resistance," Kilian told Reuters. The chief did not make clear whether Boysen was believed to have attempted suicide and said he did not immediately know the suspect's condition.
He added that no officers were hurt in the raid.
Boysen is suspected of slaying his grandparents in Renton, Washington, and stealing their car. Their bodies were found on Saturday, a day after he was released from prison where he had served a sentence for a burglary conviction.
Police surrounded the WestShore Oceanfront Motel in Lincoln City at about 11 a.m. on Tuesday, acting on a tip from a motel clerk who had recognized Boysen from images he had seen in the media, and were seeking his surrender in negotiations.
Oregon State Police said in a statement that rooms at the motel were evacuated and nearby city streets were blocked. Local residents were contacted by phone and asked to remain in their homes until the situation was resolved, police said.
Authorities had said they feared Boysen was planning to target people in positions of authority. He was released on Friday from the Monroe Correctional Facility in Washington state, after serving a nine-month sentence for burglary.
Police said the grandparents had given Boysen a room in their home. They picked him up from prison on Friday, helped him get a Washington state identification card and hosted a family party later that evening, police said.
Boysen's mother found the bodies of her parents on Saturday, according to police. The next day, the King County Sheriff's Office issued a warrant for Boysen's arrest. (Reporting by Teresa Carson; Additional reporting by Laura L. Myers in Seattle; Writing by Steve Gorman; Editing by Cynthia Johnston and Eric Beech)