Lukah Pozbeg Chang was arrested Wednesday night after a two-and-half-hour search of the Pendleton Convention Center. Police and K-9 units eventually found Chang hiding in the ceiling in a duct area between the second and third floors.
Police said they believe Chang had been hiding in the convention center for about a week.
Chief Stuart Roberts said Chang served in the Marine Corps until July 2012, and that there was an outstanding warrant for his arrest for desertion. Roberts said Chang otherwise lived an "unremarkable life," with no criminal history.
"He's lucid, articulate and responsive to police," Roberts said. "That's not the demeanor of most people we encounter in similar situations."
In run-ins with police before the Aug. 9 assault along the Umatilla River levee, Chang identified himself as Danny Wu. Roberts said the man never had identification and police had found nothing to verify what he said.
Karen Lange, 53, remains hospitalized in Portland after police said Chang beat her on the head with a piece of galvanized pipe on Aug. 9.
Her husband, Dan Lange, said on Thursday that he learned of Chang's capture first through tweets from friends, then through a text message from police. He said he texted the police back telling them congratulations.
"It was an elation that I had more so for the community of Pendleton," he said. "Just to get that weight off of our shoulders, knowing that individual was out there somewhere.
"I think it was a relief, and I was happy for the Pendleton Police Department. They had worked on Karen's case and AmyJane's case for so long. Especially AmyJane's to have the opportunity to bring this guy into custody right there in Pendleton ... and to have the opportunity as I imagine they will to interrogate him and ask what's going on. I'm happy for that."
Her son, Jason Lange, said it was good to know Chang had been captured. As of Wednesday night, he still hadn't been alerted by police.
"We're just focused on my mom getting better," he said. "That's really where all of our energy is right now.
"She is doing better - much better. She had an infection earlier this week but is recovering. That's one thing she won't have to fight."
Roberts said DNA evidence on the pipe matched DNA from a knife at last year's killing of 19-year-old AmyJane Brandhagen. She was stabbed to death at at her job in a hotel across the street from Pendleton's City Hall.
Roberts said this week that Oregon State Police would examine DNA from personal items and clothing they said Chang left behind after earlier arrests for such offenses as trespassing and living illegally along the levee. He said Chang's DNA will be placed in a database to check against other unsolved crimes.
The Associated Press and the East Oregonian contributed to this report