Jarod Lane was arrested around 3 p.m. CDT Monday near Interstate 35, said Robert Onishi with the Renton Police Department.
A passerby said he recognized Lane from recent media coverage standing alongside the interstate, attempting to hitchike, and called police. Oklahoma City officers arrived to find Lane and took him into custody.
It was not immediately clear what Lane was doing in the area.
"As to why he went down there, I don't know," Onishi said. "We know he has friends in the south, but not in that particular area."
Earlier Monday, officers in the town of Enid, about 90 miles away, were called to a Walgreens store in their city after being notified a man resembling Lane was at the store, said Sgt. Tim Jacobi with the Enid Police Department. When police arrived, the man had already left, however.
"(He) asked for a pen, asked to use the bathroom," said Onishi. "I think he had left a fairly cryptic note. They, in turn, called the police."
Lane was wanted after his ex-girlfriend, Jessica Scholl, was found dead Friday morning inside a burning home in Renton.
"Based on his actions, he was the guy who had murdered Jessica," said Onishi.
Scholl, who is a student at nearby Lindbergh High School, was found inside a home in the 12700 block of SE 164th Street after neighbors called 911 to report smoke coming from the second floor just before 8 a.m.
Renton Police Deputy Chief Erik Wallgren said firefighters arrived to find a couch on the second floor burning and the girl on the floor, unconscious. She showed no vital signs and attempts to revive her were unsuccessful.
Wallgren said the girl was the only person in the house.
Renton Police spokeswoman Terri Vickers said injuries were found on the victim's body, and police later said her death appears to be a homicide. Vickers also said the fire appears to be arson.
In a written statement released Monday evening, Scholl's family said, "We would like to take this opportunity to stress the importance of healthy relationships, and encourage everyone to report known or suspected teen or domestic violence."