PULLMAN — All four suspects have been arrested in the beating near the Washington State University campus that left a faculty member with serious head injuries.Robert D. Bean, 22, turned himself in at the Whitman County sheriff’s office at 9:20 a.m. Friday and John “Matt” Cabanos-Soriano, 22, turned himself in at 2:20 a.m. Friday at the Pullman Police Department. Both were expected to make initial court appearances Friday on possible assault charges.Earlier this week police arrested Joshua Nantz, 23, and Madeline A. Fouts, 21. Nantz and Fouts, who have been released pending charges, 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 David 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.Fouts is not suspected of involvement in the assault but is accused of rendering criminal assistance and providing false statements to police.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.