Officers responded shortly after 2 a.m. to reports of shots fired at Fair Oaks Plaza, a strip mall on East Duane Avenue in Sunnyvale's San Miguel neighborhood.
RELATED: 1 fatally shot, 1 critically injured outside Sunnyvale strip mall
It's the first homicide for the city of Sunnyvale this year.
"We're trying to find out anything, we're scouring the area for video just to see what we can find out and what occurred out here what vehicle they were in and the suspects who they were," said Captain Shawn Ahern, with Sunnyvale Dept of Public Safety.
The first arriving officer found the 21-year-old man, who was declared dead at the scene.
The second victim, a 24-year-old man, was found nearby in the parking lot and was taken to a hospital. He is in critical condition but is expected to survive, Sunnyvale Department of Public Safety Capt. Shawn Ahearn said.
Investigators believe there was "some kind of altercation" with one or more other people, but they are still seeking witnesses and surveillance video from nearby businesses.
"Obviously some sort of altercation occurred in the parking lot between these two victims and some parties how many that is, we don't know right now that's part of our investigation," SAID Ahern.
Anyone with information about the shooting has been asked to call Sunnyvale public safety officials at (408) 730-7110.
The Bay City News contributed to this report.