SPOKANE, Wash. -- Police have no suspects and no weapon in the wounding of Tony Seau, the younger brother of San Diego Chargers linebacker Junior Seau, Police Chief Roger Bragdon said Monday.

Tony Seau, 25, was shot in the head just before midnight Friday at a party in Spokane. He is in serious condition at a hospital.

"We have to do a lot of interviews," Bragdon said. "We don't know what happened out there."

Between 100 and 200 people, many of them athletes from Spokane Community College and Eastern Washington University, were at a celebration in Spokane when the shooting occurred, Bragdon said.

Seau is a defensive lineman at Eastern Washington University, located in nearby Cheney. The 5-foot-11, 310-pound nose tackle transferred to EWU in January from Palomar Junior College in San Diego County.

He was shot near the ear, Bragdon said.

Bragdon said extra police officers have been assigned to the case because he fears many of the witnesses will leave the area as college ends for the summer.

Witnesses started calling the police department Monday with details of the shooting, Bragdon said.

"There was an argument, a gunshot and many people ran away," Bragdon said, adding that Seau was involved in the argument.

Police have not interviewed Seau or members of his family, Bragdon said.

It is unclear if the shooting was gang-related, as some have suggested, Bragdon said. Witnesses told police that several arguments broke out at the party when revelers began yelling rival gang names.

"There was gang talk, but we don't know enough to say it was a gang-related shooting," Bragdon said.

Seau was upgraded from critical to serious condition Sunday

In 1993, Tony Seau pleaded guilty to attempted murder for participating in a gang-related shooting in Oceanside, the family's hometown just north of San Diego. He was sentenced to time in the California Youth Authority.