OAKLAND, Calif. (KRON/AP) — A birthday celebration ended in deadly gunfire in Oakland.

At least two shooters opened fire on a party bus driving on a San Francisco Bay Area freeway early Tuesday, killing two women and wounding at least five others, authorities said.

The passengers were celebrating a woman’s 21st birthday when the bus was attacked around 12:20 a.m. on I-580 at the Seminary Avenue off-ramp. The bus was then shot at again near Foothill Boulevard at 68th Avenue, according to police.

The family confirmed to KRON4’s sister station in Sacramento FOX40 that 16-year-old Zoey Hughes, of Modesto, and 19-year-old Alayasia Thurston, of Stockton, were killed in the shooting.

At least two shooters in another vehicle began firing at the bus, then followed it off the freeway and continued shooting at it on city streets, authorities said. About 70 rounds were fired at the party bus.

The driver of the party bus was able to pull into the Oakland Police Department’s Eastmont Station parking lot after the two separate shootings for help.

California Highway Patrol took over the investigation and said the shooting appeared to be “not random.”

At least five other women were wounded, and some were taken by ambulance to a hospital from an Oakland police station, where the bus driver went after the shooting. One of the victims is in critical condition.

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

Oakland police tweeted that a $40,000 reward would be available for information.

Last month, a 25-year-old woman was shot while riding on a party bus in Oakland. There were more than 30 passengers on the bus that was supposed to go to San Francisco, authorities said. None of the other passengers or the driver were injured, and the woman survived.

The Associated Press contributed to this report.