The shooting happened just after 12:00 p.m. Monday at a pick-up and drop-off area in front of the station.
A witness told ABC7 he heard two loud gunshots just seconds apart, coming from an area where a group of teenagers had been standing moments earlier.
Two people were hit, including one young man who was pronounced dead at a local hospital. The other victim, a bystander, is described as a middle-aged man. His injury is not life-threatening.
"There were a group of young people standing around the entrance to the Hayward BART station and there was a shooting. One teenager, a young man, went into the station, stumbled into the station, and collapsed near the station agent's booth," said Linton Johnson, BART spokesman.
The BART station was closed for most of the afternoon and did not re-open until just after 5:00 p.m.
Police are talking to witnesses who may have seen a young man walk away from the scene after the shooting, possibly carrying a gun down A Street.
Police are looking for a person of interest, described as a black male of average build in his mid-teens who wears his hair in cornrows. This person, wearing lightweight black jacket or sweatshirt with a white shirt underneath, was spotted on the Hayward station's surveillance video
BART police are asking witnesses to come forward by calling (877) 679-7000 ext. 7040.