Police sought a young gunman Sunday after a shooting the day before at a busy Seattle-area shopping mall that killed one teenager and seriously wounded another.

At least four people were detained and questioned after the shooting Saturday afternoon at Southcenter Mall, police Officer Mike Murphy said.

Murphy said the shooting stemmed from a fight between two groups of people and may have been gang related. He said police expected to identify the gunman and make an arrest soon.

The gunman and the two victims were all in their late teens or early 20s, authorities said.

The Southcenter Mall in Tukwila was jammed with thousands of pre-Thanksgiving Day shoppers when the gunman fired shots after apparently getting into a quarrel with the two victims, police said.

The mall, which covers 1.7 million square feet and includes more than 240 stores, reopened as usual Sunday morning with security officers visible.

"Clearly, such a senseless act in our community heightens everyone's state of awareness and concern. Our security precautions reflect that heightened state," mall management said in an unsigned statement Sunday.

The statement said mall owners would not comment because of the investigation but praised "the rapid response of the Tukwila police."

Investigators were trying to determine what led to the shooting and the relationship between the shooter and the victims.

SWAT teams from all over Puget Sound converged on the mall, which was locked down for six hours. Store employees and customers were allowed to exit in groups and Murphy said the shooter "must have got out with the crowd."

One victim died at a hospital. A spokeswoman at Harborview Medical Center said the wounded young man's injuries were described as non-life-threatening.