An 80-year-old driver accused of plowing her Mercedes SUV into a West Portal bus shelter and killing a family of four will continue to face four felony counts of gross vehicular manslaughter after a judge declined to reduce the charges on Friday, nearly two years after the deadly crash.
The ruling keeps the case against Mary Fong Lau on a felony track while relatives of the victims press a separate wrongful death lawsuit. Prosecutors say Lau’s 2014 Mercedes GLK accelerated to more than 70 mph and did not brake before slamming into the shelter on March 16, 2024, where the family was waiting to go to the San Francisco Zoo. The defense argued for misdemeanors, calling the crash an accident and pointing to alleged vehicle malfunction. Investigators reported no mechanical failure. The judge’s decision means Lau could face prison time if convicted.
The crash killed 40-year-old software engineer Diego Cardoso de Oliveira and his 1-year-old son, Joaquim, at the scene in front of the West Portal Branch Library. Oliveira’s wife, 38-year-old Matilde Moncada Ramos Pinto, and their 3-month-old son, Cauê, died later at a hospital. The family, originally from Brazil and Portugal, had planned a zoo visit on their wedding anniversary, relatives said. Witnesses described an SUV barreling down Ulloa Street, crossing into the transit island and shattering glass as commuters scattered. “There was no time to move,” a nearby rider said that afternoon.
During the hearing, the defense renewed its request for reduced counts, saying Lau panicked when the vehicle surged and that she has no criminal history. Prosecutors countered that surveillance and traffic-camera footage show sustained high speed with no braking and that data and inspections found no evidence of a stuck accelerator or other failure. They argued the behavior met the definition of gross negligence. The judge agreed to keep the four felony counts. Lau has pleaded not guilty. Her attorney said she is devastated by the deaths and will continue to contest the state’s characterization of her driving.
The West Portal commercial district is a compact hub where Muni trains emerge from a tunnel beside the library and a cluster of bus stops serve riders bound for the Zoo and Ocean Beach. On March 16, 2024, it was busy with families and weekend traffic when, according to investigators, Lau’s Mercedes jumped the curb and tore through the shelter. First responders triaged multiple victims as firefighters stabilized the scene. In the weeks after, city crews reinforced barriers and neighbors held vigils for the family, whose names appeared on signs taped to the shelter’s frame and bouquets set along the sidewalk. The crash sparked renewed calls for slower speeds on approaches to the transit village.
Civil filings by extended relatives accuse Lau of trying to shield assets after the crash by transferring properties out of her name. The wrongful death suit, separate from the criminal case, seeks damages for funeral costs and loss of support. Lau’s attorney has not publicly addressed the property-transfer allegations in detail but has said she intends to fight the civil claims. In court, prosecutors emphasized that the criminal case is focused on conduct behind the wheel that day, not on later financial moves, though they noted the families’ losses are central to the harm considered at sentencing if there is a conviction.
City and transit officials said camera footage from storefronts, buses and intersection systems was gathered in the days after the crash. Investigators also interviewed dozens of witnesses and pulled data from the SUV’s electronic control modules. The medical examiner found the parents died of blunt-force injuries consistent with a high-speed impact, and the infants suffered critical trauma that proved fatal despite emergency care. Police initially booked Lau on suspicion of vehicular manslaughter; prosecutors later filed four counts of gross vehicular manslaughter, reflecting the four deaths, after reviewing evidence.
The judge’s refusal to reduce the charges means the case stays in San Francisco Superior Court for felony proceedings. Next steps include an arraignment setting for continued pretrial motions, followed by readiness conferences. Prosecutors signaled they will oppose any diversion or misdemeanor plea. The defense may request a change in venue or pursue expert testing of the SUV. A trial date has not been set. In the civil arena, depositions and discovery continue, with relatives seeking records tied to any property transfers and insurance coverage that could apply. Separate hearings could stretch through 2026.
In West Portal, the shelter has since been rebuilt, but reminders of the crash remain. Shopkeepers describe quieter Saturdays in the months after and a steady stream of visitors leaving flowers near the library. “People still stop and read the names,” said a bookseller across the street. Riders recalled the sudden roar and glass as the Mercedes hit the shelter. A neighbor said he saw a passerby kneel beside a carrier holding the infant. “It’s impossible to forget,” he said, noting the corner now has heavier bollards and fresh paint on the crosswalk.
As of Sunday, Lau remains charged with four felony counts of gross vehicular manslaughter and has pleaded not guilty. A Superior Court scheduling conference is expected in the coming weeks, with a trial timeline to follow. The civil lawsuit continues on a separate track.
Author note: Last updated February 1, 2026.