SAN BERNARDINO (CBSLA.com) — The Cal State San Bernardino campus was on high alert Sunday night after campus security reported a man pretending to be a residence hall assistant and trying to convince female students to let him inside their apartments.

Students are keeping an eye out for the potential predator, who female students say knocked on their doors on Wednesday, and again on Friday evenings, around 9 p.m., claiming he was there for maintenance.

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The incidents both occurred at two separate University Village apartments.

The man is described as a tall African-American, with short, curly hair. Police have posted safety alerts on doorways.

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“We have an RA who runs the floor, and he was knocking on everyone’s door, saying ‘hey, just so you know, this is an occurrence of what happened’,” junior Zachary Holbert said.

University patrols have also increased patrols.

The alert comes after four violent incidents in March, which included attacks on women. No arrests were made in those cases.

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Detectives want to remind students that residence assistants a re required to wear a metal name badge. If students see anything suspicious, they are urged to report it to campus police.