PHOENIX -- A suspect in the death of a 21-year-old Arizona State University student has pleaded guilty to first-degree murder.Louis Eugene Harper, of Tempe, also pleaded guilty Monday to armed robbery. Sentencing is set for Nov. 7.Harper was identified as one of two suspects in the murder of Zachary Marco, who was shot as he was walking near the ASU campus in Tempe on Oct. 17, 2010. He died at a local hospital.Police believe Marco was killed for his cellphone and laptop computer. The laptop, computer bag and some papers were later recovered. Investigators said they found fingerprints from Harper and the other suspect, Marion Anthony Patterson III.Patterson pleaded guilty to second-degree murder in February. He has not been sentenced.