ALAMEDA -- The fatal shooting of a 15-year-old girl in an Alameda park, the city's first homicide this year, has stunned residents and led its police force on an aggressive search for her killer.

Ichinkhorloo Bayarsaikhan, a junior at Alameda High School, was gunned down shortly after 10 p.m. on Halloween night in the playground area of Washington Park, located at 799 Central Ave., police said.

Police believe an attempted robbery led to the shooting, which may have been carried out by five to six Asian males who were not acquainted with Bayarsaikhan or a group of 10 friends she was with at the park, according to Lt. Art Fuentes.

A police officer issuing a citation to a driver near the park was confronted by a hysteric teenage girl who said her friend had been shot.

"There was no physical confrontation between the assailants and the victim nor the witnesses other than the gunshot," he said. "The victim and the witnesses took cover and they for whatever reason left their cover. That's when the second round of gunfire occurred and that's when the victim was hit."

Officers quickly converged on the park and found the 15-year-old girl in the playground area suffering from at least one gunshot wound. She was rushed to Highland Hospital in Oakland where she was pronounced dead.

Police believe the teens got away on foot, then hopped on an AC Transit bus to Oakland before boarding BART. The 12th Street station was shut down for about an hour, but the search turned up empty.

"Everybody is quite shocked at this tragedy," Fuentes said. "We have committed our full resources to this investigation."

Investigators Thursday "secured physical evidence from the crime scene, and are "following through with additional interviews," Fuentes said.

The bus the suspects may have been on was searched. Authorities found some fingerprints, but they weren't enough to lead cops to the killer.

Police are tacking on extra patrol cars in the area of Washington Park and a police officer was patrolling the area less than a block away from where the shooting occurred, Fuentes added.

Thursday at Alameda High School where Bayarsaikhan is a junior, the mood was somber as students remembered the quiet and kind girl they called E-Ko.

"I just saw her yesterday, and I can't believe what happened," said fellow student Itzel Diaz

Thursday night Alameda residents -- some who didn't know the victim -- left flowers as their way of dealing with a crime they just can't understand.

"It's just very sad that something like this happened here," said Alameda resident Darlene Elesigue. "My kids play here. I played here as a child, and to know that something tragic like this happened -- on Halloween of all things when kids are supposed to be celebrating -- it just really breaks my heart."

"I hope that her family knows that they are not alone," said fellow resident Terri Fallon. "Alameda is pretty close knit community. I want them to know that we are all hurting for them."