Investigators were looking at stationary security cameras placed in the area that might offer more clues into the fatal attack, the Los Angeles Times reported.
LAPD Detective Sal LaBarbera said some witnesses reported hearing gunshots, but because it was raining out, there were not many people on the street at the time of the crime, early Wednesday.
"We want anyone who passed by that area [at the time of the shooting] to contact us," he said. "We have several leads we are working."
The victims were identified as Ming Qu and Ying Wu, two 23-year-old graduate students from China studying electrical engineering at the University of Southern California.
Police said after a night of studying at the library, Qu drove Wu to her home, less than a mile from campus.
The gunman approached Qu's BMW and opened fire. Wu died in the car, while Qu ran for help and was shot at again by the suspect. He was found dead on a nearby porch, police said.
LAPD Capt. Andrew Smith said investigators had little evidence in the case and were examining all motives, including that the gunman was trying to rob the pair.
The university released a statement to reassure students and employees that it was making strides to improve safety around the campus.
"Our community is saddened and outraged by this callous and meaningless act," the statement said. "Tragedies such as this morning's remind us that we all need to be continuously vigilant about safety and security."