Please answer the following question: Given the following context:  Jessica Loren, a rookie police officer on her first assignment, is ordered to take the last shift at a police station before it is permanently closed. Her mother pleads with her not to take the job, as her father, also a police officer, was killed while on duty. After assuring her mother that the shift will be uneventful, she reports for duty. Loren surprises her commanding officer Cohen, who demands that she turn around. He leads her on a brief tour, during which he explains that a HAZMAT team will be there shortly to collect evidence that is difficult to dispose of and that she is not permitted to leave her post. Before he leaves, he gives Loren his phone number in case of emergency. Loren becomes bored and almost falls asleep, though she wakes when she hears knocking. She does not see anyone at the door but turns around to find a homeless man standing in the hallway; he urinates on the floor and refuses to leave. Loren takes him to a holding cell, where the door suddenly closes and locks behind her. The lights go out, a bloody-faced person surprises her in the door's window, and she drops her flashlight. An unidentified person picks it up and taunts her. When the lights come back on, the door opens and no one is there.  answer the following question:  What is the last name of the person who tells Jessica not to leave her post?
A:
Cohen