Police say the suspect walked into Alamitos Hall on Thursday night and targeted a student in his dorm room.
"He had left the door open and the suspect walked in, brandished a gun and then demanded his belongings. He had also briefly bound the student," said Cal Poly Pomona Spokesperson Uyen Mai.
The suspect stole a computer and other personal items. He is described as a black man in his mid-20s, 6 feet 2 inches tall with a medium build, short hair and an unshaven face.
Police say the description is similar to that of a suspect who robbed two students in parking lot B on the campus last Sunday night. In that case, the suspect lifted up his shirt to reveal a gun in his waistband.
"It's really close to where we are and it's on campus, so I guess I'm a little scared now," said student Melanie Jackson.
According to student Spencer Keller, who lives in Alamitos Hall, a key is required to enter the building. But he says the suspect could have easily followed other students inside.
Campus police are stepping up patrols and Cal Poly is encouraging students to report any suspicious activity, use the buddy system and to be alert.
Cal Poly wants anyone with information on the suspect to contact University Police at (909) 869-3070.