HOUSTON -- Even though police are patrolling the grounds, an unsettling mood has taken over the University of Houston campus.

"Its hard to imagine that something like that happened in this parking lot because I use this parking lot," said Vasduha Segal.

Several students are fearful after news spread that two students were robbed at gunpoint within the last two weeks.

"You're always kind of on the edge when you're walking, especially at night or it gets late," said Chinmaya Gupta.

In the first robbery on Jan. 26, campus police said a student was held up in one of the school's parking lots. Investigators said the victim was meeting a man he had sold and old cellphone to on Craigslist, because he was trying to sell an old cell phone. But when the man showed up to the school, authorities said, he pulled out a gun, threatened the student and then took off with his cell phone and his car keys.

"I live on campus and I have classes late at night so … it's kind of scary that at any time of the day -- morning, noon, or night -- something like that could happen," said Enegah Bate.

On Thursday, another thief robbed another student in another parking lot, detectives said.

Police said the student was robbed of her iPhone near Cullen Boulevard as she made her way to her car. Officials said the man pretended he needed to borrow the girl's phone and then pulled out his handgun.

Now many are left wondering what will happen next if these thieves aren't caught.