The three soldiers, whose names had not been released, are suspected of killing Spc. Tevin Geike, 20, of Summerville, S.C. All four are from Joint Base Lewis-McChord.
County Prosecutor Mark Lindquist said the trio of suspects are expected to be charged and make an initial court appearance Tuesday, The Seattle Times reported.
Lindquist said it appeared "there was only one individual who stabbed the victim." The newspaper said it was unclear what roles the other two played in Geike's death.
One suspect is 23 and the others are 21. The 23-year-old is suspected of having stabbed Geike. His motive wasn't known.
Geike, who had been in the Army since October 2010 and stationed at the Washington base in April 2011, was killed Saturday in Lakewood.
While police had said during the weekend the slaying was being investigated as a possible hate crime, Lakewood police said in a release that race was not believed to have been a factor.
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