OAKLAND, Calif. (AP) — Authorities say someone has opened fire on a party bus on a San Francisco Bay Area freeway, killing two women and wounding at least three others.

The East Bay Times reports that the passengers were celebrating a woman’s 21st birthday early Tuesday when the bus was attacked as it was returning to Oakland from San Francisco. Dozens of rounds were fired at the party bus.

The California Highway Patrol says “it does not appear this shooting was a random event.”

Relatives told the newspaper that one of the women killed was a 19-year-old Stockton resident.