SAN FRANCISCO (KRON) -- San Francisco's police chief and district attorney said a driver who allegedly killed an entire family at a West Portal bus stop will be charged with vehicular manslaughter. A family of four was waiting at the bus stop to go to the zoo when an SUV plowed into them March 16. Investigators said the driver, 78-year-old Mary Fong Lau, was speeding and driving the wrong-way into oncoming traffic when her white Mercedes SUV jumped a sidewalk curb and crashed into the Muni Metro West Portal Station. Diego Cardoso de Oliveira, 40, his wife Matilde Moncado Ramos Pinto, 38, and their two children, 1-year-old Joaquin Ramos Pinto de Oliveira, and 2-month-old Caue Ramos Pinto de Oliveira were killed. Diego Cardoso de Oliveira, Matilde Ramos Pinto, and their young children pose for a family photo. (Photo courtesy the Pinto and Oliveira family) After the crash, Lau was hospitalized, arrested, and released from custody. On Tuesday, SF District Attorney Brooke Jenkins explained to reporters why it took three months for any charges to be filed. "I want to thank the public and the (victims') family for their patience in allowing the police department to conduct a very thorough investigation. Of course everybody wants to know the outcome. A part of the investigative process was to flush out alternative causes for why this happened. We wanted to make sure that there was not some type of medical issue, or a (mechanical) issue with the vehicle ... to make sure they were not factors in causing this collision," Jenkins said. Matilde Ramos Pinto, left, and Diego Cardoso de Oliveira, right, are seen in a photograph left at a bus stop memorial. (KRON4 image) Jenkins said her office will file four felony counts of vehicular manslaughter against Lau -- one count for each family member's death. The collision was caused by "gross negligence" committed by the driver and "excessive speed," Jenkins said. "We looked at every aspect of the collision," SFPD Chief Bill Scott said. The driver was not under the influence of drugs or alcohol, Scott said. Mechanical failures were also ruled out as factors. An SUV crashed into Muni’s West Portal Station, killing three family members on Saturday, March 16, 2024. (Benjamin Fanjoy /San Francisco Chronicle via AP) Lau was re-booked into jail on Tuesday evening, jail records show. She is being held in lieu of $150,000 bail. Scott said the deaths of an infant, a baby, and their parents were "horrific," and the incident impacted the "entire city of San Francisco." He added, "A lot of people were traumatized by this incident. Four lives were lost. That's what is (weighing) on everybody's heart." Woman who died after being pushed into SF BART train identified The victims' family wrote in a previous statement to KRON4, "Diego and Matilde were warm and loving parents who had a deep love for their beautiful children and enjoyed nothing more than spending time with their two little boys. They were also what one would call real ‘life enhancers’ — the kind of people everyone loved to be around."