One man was killed and another was listed in critical condition Sunday after two separate shootings this weekend in the San Fernando Valley, police said.

The first shooting occurred Saturday around 9:40 p.m. in the 8700 block of Langdon Avenue, in Panorama City when a suspect in a dark sedan opened fire and an "innocent bystander" was shot, said Officer E. Heinzman, of the Los Angeles Police Department's Mission division.

In what was described as an exchange of gunfire, the man in a nearby vehicle was shot in the head, Heinzman said. He was rushed to a local hospital where he was in critical condition.

Heinzman said she was uncertain if the suspect was shooting at people in another vehicle or pedestrians on the street.

No suspects have been identified, and there was no other information about the victim.

In a separate incident, Vartan Avatyan, 18, of North Hollywood was shot and killed early Sunday at a popular taco stand.

"As they stood in the parking lot, a male Hispanic walked up to the small gathering of friends and began shooting at Avatyan, striking him several times," police said.

The shooting occurred at 12:40 a.m. at the taco stand in the 7200 block of Lankershim Boulevard in North Hollywood. Avatyan was taken to a local hospital in critical condition, but died a short time later.

The suspect is believed to have left the area in a blue compact car.

Detectives have very few leads in the case and are asking for anyone with information to contact LAPD North Hollywood homicide detectives at 818-623-4075. During non-business hours or weekends, calls may be directed to 877-LAPD-24-7. Anyone wishing to remain anonymous can call Crime Stoppers at 800-222-TIPS.