A man with an extensive criminal past was being sought Sunday as a "person of interest" in an ambush on four police officers who were killed inside a coffee shop in Parkland, Wash.

Pierce County sheriff's spokesman Ed Troyer told reporters that Maurice Clemmons, 37 years old, was one of several people investigators want to talk to and that he couldn't be called a suspect at this point.

In a news release, the sheriff's office said Mr. Clemmons has an extensive violent criminal history from Arkansas and recently was arrested and charged in Pierce County in Washington state on suspicion of third-degree assault on a police officer and second-degree rape of a child. He was released from custody six days ago, according to the Seattle Times.

In 1989, Mr. Clemmons, then 17, was convicted in Little Rock of aggravated robbery. He was paroled in 2000 after then-Gov. Mike Huckabee commuted Mr. Clemmons's 95-year prison sentence.

In Parkland, the four officers were just starting their shifts and were at the Forza Coffee Company shortly after 8 a.m., said Brandy Kessler, a spokeswoman for the Washington State Patrol.