The attacker was waiting.
The Penn student was leaving her third floor apartment when the attacker grabbed her at knifepoint and forced her back inside. He then bound, blindfolded, and gagged her.
A short time later the victim's roommate arrived home.
"The male then sexually assaulted this victim inside the apartment, repeatedly over a period of time. She was also blindfolded, gagged, and bound with duct tape," Captain John Darby of the Special Victims Unit said.
The attack has women in this West Philadelphia neighborhood feeling scared and vulnerable.
"I'm going to make sure I lock my doors when I go home tonight," Melissa Baker said.
Investigators believe the predator may be linked to other attacks, including a home invasion, sexual assault, and robbery of a man and his girlfriend at the Clinton Court apartments at 9th and Clinton Streets in October.
"In all four victims' cases, they are bound, not for moments, but literally, in terror for hours," Captain Darby said.
Detectives say in this most recent attack, he stole a Dell Computer, two iPod Nanos, jewelry, and other items.
They believe he may be trying to sell the goods.
They also want you to take a close look at the sketch to get the culprit off the streets.