Investigators have identified no suspect in Tuesday morning's shootings near Balboa Avenue but have narrowed down the time of the gunfire to 7:15 a.m., CHP public affairs Officer Allen Reyes told reporters.

One of the bullets passed through a passenger door on a southbound Toyota Matrix driven by 21-year-old University of San Diego student Ashley Simmons and struck her in the rib cage area. Simmons, who was able to keep driving and apparently didn't immediately realize she'd been shot, underwent emergency surgery and is expected to recover.

The next morning, a 42-year-old Rancho Bernardo man contacted the Highway Patrol and reported that his car apparently had been struck by a bullet on the same stretch of freeway at about the time the young woman was wounded. Authorities confirmed that the man, who was uninjured, was also the victim of a shooting.

Officials believe the same assailant opened fire on both victims.

The Highway Patrol has received "a myriad of phone calls" offering tips in the case, Reyes told news crews late Thursday afternoon outside the CHP's San Diego station on Pacific Highway.

"We do have a team of investigators working diligently on the case, and every call is being evaluated for credibility and to determine if ... they are, in fact, associated with this incident," he said.

Reyes said they're asking anyone who saw anything suspicious on the right shoulder of the freeway between Clairemont Mesa Boulevard and Balboa Avenue to come forward. He said something deemed suspicious would include a possible disabled vehicle along the road.

It remains unclear if the victims, whose names have not been released, were targeted or were struck by random gunfire.

"The investigation at this point is not confirming either way," Reyes said.

Reyes said the 10 bullet casings found near the scene are still undergoing testing. He would not say what type of weapon was used.

Reyes urged drivers not to panic, but said they are welcome to take another route if that makes them feel safer.

Any tipsters are asked to call the CHP at 619-220-5492.