A third young man and a young woman were earlier arrested and released.
No one has yet been charged in the March 30 beating of instructor David Warner, who is recovering in a Spokane hospital from a beating he suffered near the WSU campus in Pullman. Police say he intervened in an argument.
Robert Bean, 22, of Mukilteo, and John "Matt" Cabanos-Soriano, 22, of Everett, appeared in Superior Court but were released because they had no criminal history and were unlikely to flee, Whitman County Deputy Prosecutor Bill Druffel told The Spokesman-Review.
They were taken into custody earlier Friday for investigation of first-degree assault.
Earlier this week police arrested Joshua Nantz, 23, of Pullman, also for investigation of first-degree assault. Madeline Fouts, 21, was arrested for investigation of rendering criminal assistance. Both have been released.
Nantz and Fouts are students, said WSU spokesman Robert Strenge. Cabanos-Soriano and Bean are not students, he said. The four are friends, police said.
Cabanos-Soriano, Bean and Nantz are suspected of assaulting Warner during an argument about 2 a.m. March 30 in a parking lot outside of Adams Mall on College Hill in Pullman. Adams Mall houses a market and bar and is popular with students because it's close to campus fraternities.
Warner, 41, was in critical condition until he was upgraded to serious condition Thursday at Sacred Heart Medical Center in Spokane. He remains in the intensive care unit, hospital spokeswoman Pattie Servine said Friday.
Warner is Native American and teaches in the WSU Department of Critical Culture, Gender, and Race Studies. He holds a doctorate degree and is a non-tenured instructor, Strenge said.
Warner was intervening in an argument between an acquaintance and a group of college-age people when he was beaten, said Pullman police Cmdr. Chris Tennant.
"Warner was not the aggressor. He was in a peacekeeper role. He had his hands up in the air, obviously trying to break up an argument," Tennant said.
The acquaintance was not injured. What led to the fight is still under investigation. Alcohol was involved and everyone has their own perceptions of what happened, Tennant said.
Police received an anonymous tip in the form of a letter, identifying the four who have been arrested, The Spokesman-Review reported.
Druffel said he hopes more witnesses come forward.
"Since the break in this case, many people have come forward and we're getting new information all the time," he told the newspaper. "I need that to continue so we can make a careful and deliberate decision."
WSU President Elson Floyd announced a Commission on Campus Climate on Tuesday to address what he called "an underlying fear and anger among some on campus regarding issues of race and marginalization."
"Initially there was really a concern this might be hate crime. I think that has declined as facts have come out," Strenge said.
"A segment of the student population has very strong feelings - expressed primarily on Facebook," Strenge said. Floyd "feels this situation revealed concerns among a segment of the student population that need to be addressed."