Tacoma Police Department stated on Twitter that two males and one female died at the scene, and that a male was admitted to hospital with life-threatening injuries.
Later, police said that the victim had died from injuries sustained while being taken to hospital. According to The News Tribune, the victims were adults.
The shooting took place in Salishan, on the city's Eastside.
Haddow said that investigators aren't certain if the shooter was acting alone. At 7:07 p.m., there was no arrest or public identification.
She said that detectives and crime scene technicians had erected blocks around the scene to prevent them from capturing evidence.
Haddow stated that there have been 27 homicides this year in Tacoma. It has approximately 212,000 residents.