Four robberies occurred near the University Park Campus in the past two weeks, and at least two cases involved firearms, according to the USC Department of Public Safety.

As a result, DPS is asking students to not walk alone off campus, especially after dark. David Carlisle, DPS assistant chief, said the department advises students to pay attention to their surroundings and to not expose their cell phones in public.

"I know it's very, very common, but particularly if you [are] by yourself, don't do that," Carlisle said.

Carlisle said that based on suspects' descriptions, three of the four cases probably were related. He added that the two latest incidents occurred the morning of April 3, around 10:20, north of campus near the Shrine Auditorium.

DPS believes that the robberies happened back to back at the top and bottom of 32nd Street. In both cases, the robbers brandished a handgun.

"It's unusual for a robber to display a gun, especially so early in the morning," Carlisle said, "They were obviously driving around USC looking for students by themselves, who were on their cellphones."

Two other cases happened on March 31, one on Ellendale Place and another on 32nd Street.

"The common denominators in these robberies are students walking alone not paying attention to their surroundings or talking on their phones," Carlisle said.

He said DPS has the footage of the robbers' car, which lacked license plates. The Los Angeles Police Department is working with DPS to apprehend the robbers and implement preventative measures in the affected areas.

Carlisle added that the university has increased USC Security Ambassador presence and LAPD has deployed additional officers to patrol the area. Additionally, DPS is having the camera operators focus their cameras where the crimes are occurring.

There are 40 security ambassadors deployed strategically in the North University Park neighborhood every day from 4 p.m. to 6 a.m. Their placements were determined by student walking patterns and where crimes occur throughout the day.

"We can't afford to have them at every corner," he said.

Security ambassadors were not on site at the time of the robberies because they happened so early in the morning, but Carlisle said DPS has adjusted coverage to be closer to 32nd and Royal Street where the robberies occurred. Recent criminal activity, however, has been in broad daylight, which has prompted the ambassadors to start patrolling earlier.

The security ambassadors' duty is to observe and report. If they see a robbery in progress, they are not supposed to confront the suspects and can only contact DPS.

DPS said it has received calls from concerned parents due to fear among some students. However, Carlisle said the department is confident that the suspects will eventually be caught.