A red Honda coupe driven by 43-year-old Raul Padilla appeared to have slammed into the center divider of U.S. 101 before it came to a stop facing oncoming traffic, California Highway Patrol Officer Art Montiel said.
After the Honda stopped, the front end of the party bus, which had 18 people on board, hit the disabled car. Two other cars were also involved in the collision.
"We're still trying to figure out who came into contact with what," Montiel said.
The woman killed was a 36-year-old passenger in the Honda and married to Padilla. Her name has not been released while officials try to contact other family members.
Padilla was hospitalized in critical condition. He was wearing his seatbelt, but his wife was not, according to the CHP.
Padilla and his wife had "consumed alcohol" before the crash, but toxicology tests would have to be conducted to determine if Padilla had been driving under the influence of alcohol at the time of the crash, Montiel said.
"If it is determined he was under the influence, he could face felony DUI charges and manslaughter charges," Montiel said.
Initially, based on their driver's license information, authorities had said the woman was from San Mateo and Padilla was from Oakland, but the information may have not been updated, Montiel said.
The bus was equipped with seatbelts, but Montiel did not know how many, if any, of the passengers were wearing them at the time of the crash. Bus passengers in California are not required to wear seatbelts, Montiel said.
The bus was towed to an impound yard, but Montiel did not know the name of the company.
The drivers of the two other vehicles involved in the Redwood City crash, about 25 miles south of San Francisco, were not hurt.
The southbound direction of U.S. 101 was closed for about two hours after the crash, with traffic being diverted to city streets.
The crash comes just three weeks after five women heading to a bridal party were killed just a few miles away in a limousine fire on the nearby San Mateo Bridge.