Known to her loved ones as Katie, Katherine Elizabeth Mannix was a 24-year-old woman with a playful attitude and a big heart, remembered for her beautiful smile and "quirky Katie-ism's." Born in San Francisco on November 11, 2001, she grew up in Marin County, graduating from Redwood High School in 2020. After high school, she spent time in Santa Barbara, creating a community of lifelong friends before returning to Marin.
Following in her older sister's footsteps, Katie was a second-year nursing student at the College of Marin and was already helping others through clinical rotations and a job as a Certified Nursing Assistant at a local hospital. Her family remembered her love for completing daily arts and crafts projects, trying new restaurants with her siblings, and playing with her new kitten, Suki. A cousin recalled how she would send random texts just to say she loved you or to offer encouragement. Her uncle described her as a strong, independent, and outspoken young woman who, like her mother, was not afraid to bring up a different perspective.
The evening of Sunday, October 11, 2026, ended in tragedy at the family’s home in an affluent, unincorporated area of Mill Valley, CA. Shortly after 5 p.m., a 911 call was placed from the residence on Strawberry Circle reporting gunfire. The caller, one of Katherine’s adult siblings, had been inside the home and escaped to safety. According to law enforcement radio communications, the reporting party stated that "the father killed the mother and the sister" with a handgun.
When deputies from the Marin County Sheriff's Office arrived within minutes, they secured the area and entered the house. Inside, they discovered the bodies of three people, all deceased from gunshot wounds. The victims were identified as Katherine, her 65-year-old mother, Ann Elizabeth Mannix, a retired and highly decorated Deputy Chief of the San Francisco Police Department, and her 68-year-old father, Kevin Mannix, a retired SFPD sergeant.
The Marin County Sheriff's Office immediately began an investigation. Based on the preliminary evidence at the scene, detectives determined the incident was a double murder-suicide. Investigators concluded that Kevin Mannix shot and killed his wife, Ann, and their daughter, Katherine, before turning the gun on himself. At the time of the shooting, Ann and Kevin were estranged and in the process of a divorce. The sheriff's office assured the public that there was no ongoing threat to the community. Autopsies were scheduled for the following Tuesday.
The violent deaths sent shockwaves through the law enforcement community and beyond. San Francisco Police Chief Derrick Lew sent a department-wide message expressing his sorrow, stating, “My heart goes out to all their family members, friends and colleagues at the SFPD as we all work to process this tragedy.” The San Francisco Police Officers Association released a statement saying the SFPD family was "reeling" from the "horrific and senseless" loss. San Francisco Mayor Daniel Lurie also expressed his condolences, noting Ann Mannix's trailblazing career.
In the days that followed, a memorial of flowers and notes grew outside the family home on Strawberry Circle. Family and friends mourned the immense loss of both a pioneering police official and a young woman just starting her life of service. Ann’s brother, Richard Corriea, remembered his niece’s independent spirit and love for her family. A joint funeral Mass for Katherine and her mother was held on Friday, October 23, 2026, at Saint Ignatius Church in San Francisco. A funeral fund was also established for the family.
As of October 2026, the investigation by the Marin County Sheriff's Office officially concluded that Katherine and her mother were victims of a murder-suicide committed by Kevin Mannix. The case is considered solved, with the primary suspect deceased.
