3 Dead, 1 Injured, at House Party Shooting in Seattle Suburb

A suspect is in custody, officials said.

A suspect -- apprehended in Lewis County, south of Seattle -- is in custody, the city of Mukilteo tweeted.

"There was a shooting tonight in the Chennault neighborhood," the city tweeted at 2:40 a.m. local time, subsequently adding that between 15 and 20 people were present at the home.

Thirty minutes later, the city tweeted, "We are sad to report 3 fatalities tonight, 1 injured and transported to Harborview [Medical Center in Seattle], we do not know the extent of injuries."

The victims' names will not be released until they are identified and next of kin are notified, officials said.

Local police said it also established a "reunification center" for parents and relatives of party-goers at a local church.

ABC News' Alex Faul, Rex Sakamoto, Devin Villacis contributed to this report.