The shooting broke out just after 1 a.m. at Munchbar at Bellevue Square, an upscale shopping center about 10 miles east of Seattle, said Carla Iafrate, a spokeswoman for the Bellevue Police Department.
Police officers were outside the bar when gunfire erupted because a large crowd had gathered there, she said.
More than 600 people were inside the venue at the time of the shooting. "It was a very complicated scene," Iafrate said.
The wounded man was taken to Overlake Medical Center in Bellevue. Iafrate did not immediately know his age, hometown or condition.
The shooting appears to be an isolated incident. "There was some type of altercation," before it, she said.
Iafrate said the suspect police are seeking, Ja'mari Alexander Alan Jones, was convicted as a juvenile in the high-profile 2008 beating death of a Seattle street performer. Jones was sentenced to less than a year in juvenile detention on a first-degree manslaughter charge in that case.