Updated

A shooting targeting a party bus on a San Francisco Bay Area freeway early Tuesday, killed two women and wounded at least three others, according to reports. 

The passengers were celebrating a woman’s 21st birthday when the bus was attacked around 12:20 a.m. Tuesday on Interstate 580 as it was returning to Oakland from San Francisco, the East Bay Times reported.

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A shooter or shooters in another vehicle began firing at the bus and then followed it off the freeway and continued shooting at it on city streets, authorities said. Dozens of rounds were fired at the party bus.

"Based on preliminary investigation, it does not appear this shooting was a random event," according to the California Highway Patrol, which is investigating along with Oakland police.

At least three women were wounded and taken by ambulance to a hospital from an Oakland police station, where the bus driver drove after the shooting.

One of the women killed was a 19-year-old Stockton resident, relatives told the newspaper. The Alameda County Coroner’s Bureau said one woman died on the bus and the other at an Oakland hospital.

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A man who identified himself as the father of the 21-year-old celebrating her birthday said his daughter was shot in the leg but is in stable condition.

The Associated Press contributed to this report.