Police surrounding a motel on the Oregon coast are using a loudspeaker to try to persuade a man inside to surrender.

Police on Tuesday said they believe the man in the motel is Michael Boysen, who is suspected of killing his grandparents last weekend in Renton, Wash.

Two loud bangs could be heard at the motel in Lincoln City early Tuesday afternoon. It was not clear what caused the bangs.

Police had sent a small robot up some stairs and onto a balcony of the motel before the blasts. A loudspeaker was used to tell the suspect to throw down his weapons and surrender.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

Authorities say a man who killed his grandparents in their Seattle-area home, triggering a multistate manhunt, may be barricaded in a hotel on the central Oregon coast.

The King County Sheriff's Department said on its Twitter feed Tuesday that police in Lincoln City, Ore., had surrounded a hotel where 26-year-old Michael "Chadd" Boysen was believed to be. Police say Boysen killed his grandparents in their Renton house after his release Friday from prison. Authorities haven't said how they died.

Oregon State Police spokesman Gregg Hastings said in an email that troopers were helping Lincoln City police negotiate the safe surrender of the suspect. Other rooms at the Oregon hotel had been evacuated, surrounding streets closed off and nearby residents were told to remain in their homes.

About two blocks down the street from the police presence in Oregon, Ann Chapatte, manager of the Overlook Motel, said she had been watching through her binoculars, and could see about 10 police in camouflage gear with guns drawn around the Westshore Oceanfront Motel.

She said she could see six cars from state police, Lincoln County Sheriff's Office and Lincoln City Police, as well as a big SWAT team vehicle and a little robot. No shots had been fired. And traffic was blocked off.

Police have been there since about 10:30 a.m., she said.

"They are dressed in their camouflage and they've been pointing their guns at we're not sure which building," Chapatte said.

Boysen made threats against members of his family and law enforcement while behind bars, Corrections Department spokesman Chad Lewis said Tuesday. But authorities didn't learn of the threats until after the bodies of the couple were found Saturday and the manhunt had begun.

"Sources went to our staff at the Monroe Correctional Center and told us he had been threatening to do all this," Lewis said Tuesday.

The information was passed on to King County deputies and that's why King County Sheriff John Urquhart called Boysen extremely dangerous at a Monday news conference.

Investigators have also determined that Boysen searched the Internet for gun shows.

Boysen just finished serving nine months in prison on a burglary conviction, Lewis said. He had no violent infractions in prison - "nothing extraordinary," Lewis said.

From 2006 to February 2011, Boysen was in prison for four robbery convictions, Lewis said. The robbery convictions were related to an addiction to narcotic painkillers, Lewis said.

The grandparents picked him up from prison at Monroe Friday, drove him to meet his probation officer and to get an identification card from the Department of Licensing and held a welcome home party for him Friday night.

He was going to stay with the couple at their home.

The bodies were discovered by Boysen's mother Saturday evening. She had been called by a family member who became concerned that the couple hadn't answered their door.

The motive for the killings remains unknown, King County sheriff's Sgt. Cindi West said.

"Between the family and detectives we have no idea," West said. "It's just bizarre. The family loved and supported him the whole time he was in prison."

The King County medical examiner's office has not released their names. Family and neighbors told KOMO News they are Robert R. Taylor, 82, and Norma J. Taylor, 80.

Boysen is white, 5-foot-7, about 170 pounds. Police said he might be driving his grandparents' car, a red 2001 Chrysler 300 with Washington license 046XXU.

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Associated Press writer Jeff Barnard contributed to this report from Grants Pass, Ore.