Officials at the scene told The News Tribune in Tacoma two gunmen burst into the Forza Coffee Co. and shot the four uniformed officers as they were working on their laptop computers, then fled the scene.
Pierce County Sheriff's spokesman Ed Troyer said investigators believe the officers were targeted, and it was not a robbery.
Troyer tells the newspaper "it was just a flat out ambush."
He could not immediately say what agency the officers were from. Police were searching for two suspect and interviewing witnesses. The coffee shop is near McChord Air Force Base in Tacoma, about 35 miles south of Seattle.
"We hopefully will have answers, but there is nothing more we can tell you," Troyer told KING-TV. "That's as cold-hearted as it is."
Roads were blocked around the attack. A witness driving past told the newspaper he saw an officer on the ground just after the shootings.
Last month, Seattle police officer Timothy Brenton was shot and killed Halloween night as he was sitting in a cruiser with trainee Britt Sweeney. Sweeney was grazed in the neck.
Christopher Monfort, 41, of suburban Tukwila, was charged in the shooting. Days after the shooting, Seattle detectives attempted to question Monfort at his residence. Police say that Monfort then ran from the detectives and tried to use a gun. The detective shot him.
Authorities also linked Monfort to the October firebombing of four police vehicles, with prosecutors saying Monfort waged a "one-man war" against law enforcement.
Monfort remained hospitalized.