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SAN FRANCISCO, Nov. 23 (Xinhua) -- Two boys were shot and killed Saturday at an elementary school in Union City, Northern California, the Union City Police Department (UCPD) said.

The UCPD confirmed the victims were two males, aged 11 and 14, who were sitting in a van in the west parking lot of Searles Elementary School in Union City after they "were confronted by unknown suspect(s) who shot into their vehicle multiple times."

One boy was killed instantly and the other died when he was transfered on the way to a local trauma center, said the police, who declined to reveal the names of the victims because they are minors.

The police said an investigation is being conducted into the incident for possible motives, and no suspects have been arrested.

It was the second shooting incident in the city in a week. In the previous similar shooting, two men were wounded in a shooting on Wednesday on a street in Union City, and they were released after being treated at a local hospital.

The police said no evidence indicated the two incidents were linked, but they did not rule out that possibility.

The UCPD is currently verifying whether Saturday's killing is related with gang violence.