A killer, armed with a handgun, unleashed a volley of shots killing four police officers in a coffee shop in Washington and escaped.
The four police officers, three men and a woman, were wearing bullet proof vests, but did not have the time to return fire at the coffee shop located near McChord Air Force Base in Washington.
The attack immediately raised fears of a repeat of the massacre at Fort Hood military base in Texas, where Major Nidal Hasan killed 13 people on Nov 5.
The gunman burst into the Forza coffee shop, which is on a side street next to the base in Tacoma, Washington, 40 miles south of Seattle. The police officers were working on laptops preparing paperwork ahead of their shifts when the gunman attacked at 8.15 am local time.
Police said the officers were deliberately targeted and the attack was not a robbery that went wrong. "This was more of an execution. Walk in with the specific mindset to shoot police officers," said Ed Troyer, the Pierce County Sheriff's spokesman.
"There were marked patrol cars outside and they were all in uniform." He said the gunman is believed to have walked in alone but the possibility of an accomplice has not been ruled out.
Police said they believed one of the officers wrestled with the suspect and may have shot him.
Troyer said: “We believe there was a struggle in there and there is a possibility one of the officers may have fired a shot. We hope that he hit him. If he did, then he is injured.”
He appealed for information about anyone who had been seen in the area with a gun wound. The suspect was described as black, in his 20s or 30s and "scruffy".
Describing the scene at the coffee shop, Troyer said: “It's carnage out front everywhere. It's like a bad horror movie. It's horrible.”
There was also speculation that the attack could be a copycat shooting after another officer, Timothy Brenton, was shot and killed last month while sitting in a car.
Authorities say the man charged with that shooting also firebombed four police vehicles last month as part of a "one-man war" against police.
Christopher Monfort, 41, was arrested days after the Seattle shooting and remains in hospital in a stable condition.
Troyer said: "We won't know if it's a copycat effect or what it was until we get the case solved. We don't even have a suspect ID right now." Two baristas and several customers were in the coffee shop but were not shot.
Troyer said: "Some are in shock. They are very upset. They are the ones who are going to put together for us how this happened."
Police later seized a pickup truck parked in a nearby grocery store.