Story highlights The suspect has apparently self-inflicted cuts, a police chief says

No other injuries are reported as authorities go into his room, he adds

Michael Boysen's grandparents picked him up from prison; they were later found dead

He later checked into a motel on the Oregon coast, where a clerk noticed him

A standoff at a beachside Oregon motel ended Tuesday evening with the focus of the police's attention -- the suspect in his grandparents' deaths over the weekend -- being taken from his room and transported away in an ambulance.

Members of a "tactical team" entered the Lincoln City, Oregon, room of 26-year-old Michael Boysen around 7 p.m. (10 p.m. ET), emerging with no injuries, said city police Chief Keith Kilian. The suspect had suffered apparently self-inflicted cuts, he added.

The image of him on a stretcher being placed in a waiting ambulance closed a day full of drama at the WestShore OceanFront Suites.

Boysen was taken into custody about an hour after authorities used water cannons to blast down part of the front door to the suspect's room, a move that showed authorities' intent to "just kind of step ... things up a little bit," according to Kilian.

"We removed the front door for him to show him which way we wanted him to come out," the police chief told reporters a short time later. "And he chose not to."

Boysen was released last Friday from the Monroe Correctional Facility in Washington state, where he served a year behind bars for burglary.

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His grandparents picked him up, drove him around running errands and held a gathering for family members at their home to welcome him back, said King County Sheriff John Urquhart.

The next day, the grandparents were found dead.

After Boysen and his grandparents did not respond to phone calls Saturday, his mother drove over with a key to the house in Renton, Washington, near Seattle, and found the couple's bodies.

Boysen and his grandparents' car were missing.

Authorities have not said how the victims were killed. A gun was not used, but the deaths were violent, they said.

During the course of their investigation, detectives said they learned that Boysen had talked about killing his grandparents, acquiring guns and going after authority figures. He had searched the Internet for gun shows across the Pacific Northwest and Nevada.

"We need to do everything we can to get this man off the street as soon as possible," Urquhart said. "His threats against authority figures make him very dangerous and unpredictable."

Boysen checked into the WestShore OceanFront Suites, situated along the Pacific Ocean, around 10 or 10:30 p.m. Monday, said Killian.

The hotel clerk contacted police around 7:30 a.m. Tuesday after watching a news broadcast and identifying Boysen by face and by name. Police arrived soon thereafter, and an Oregon State Police SWAT team and hostage negotiator were on site by 10:45 a.m.

With nearby roads blocked off, armored personnel trucks were stationed in the hotel's parking lot, while at least one sniper was positioned with clear sight of the suspect's room, according to video from CNN affiliates at the scene.

The police chief said the suspect had barricaded his door, so even after the water cannons were used "it didn't come down all the way."

"His request was for us to go away and leave him alone," Killian said then of authorities' initial communications with the suspect. "Obviously, we're not going to do that."