A gunman who killed three people, in what US police said was a random attack, telephoned his mother and then shot himself dead Tuesday in the state of Washington.

The dismaying episode came on the heels of two mass shootings in California that have left 18 people dead as the United States grapples yet again with the horror of spiraling gun violence.

Police in Yakima say a man they earlier named as 21-year-old local Jarid Haddock shot people in and around a convenience store overnight, before fleeing.

Officers launched an extensive manhunt throughout the city of 100,000 people, which sits 100 miles (160 kilometers) southeast of Seattle, warning that the wanted man was armed and dangerous.

"It appears to be a random situation," Yakima Police Chief Matthew Murray said early Tuesday.

"There was no apparent conflict between the parties. They just walked in and started shooting."

Hours later police received a 911 emergency call from a woman who said the wanted man had borrowed her phone.

"He then called his mother and he made several incriminating statements including 'I killed those people'," Murray told reporters.

"He made several statements in front of her that he was then going to kill himself."

First responders raced to the scene near a supermarket, arriving in time to hear gunshots as he killed himself.

"They gave medical care tried to save his life, but he was later pronounced deceased."

The shooting in Yakima was the latest spasm of gun violence to shake the United States.

On Monday, seven people died at two agricultural sites south of San Francisco when a Chinese-American farmworker is believed to have opened fire on his colleagues.

Some of his victims are known also to be Chinese.

On Saturday night, an elderly Asian man rampaged through a dance studio in Monterey Park near Los Angeles, killing 11 people who had gathered for Lunar New Year celebrations.

Huu Can Tran shot himself dead several hours later as police moved in on his van.