Margaret Mamer, 61, was butchered with a knife and hacksaw by her roommate Lisa Gonzales in their San Francisco home after she refused to move out or pay rent, authorities said.
Background
Mamer had been living in the home on 14th Street when tensions escalated with her roommate Gonzales over unpaid rent. A third roommate told investigators that in mid-April 2018, Gonzales gave Mamer 30 days' notice to move out. When Mamer refused to leave, prosecutors said Gonzales took matters into her own hands.
On May 15, 2018, the situation took a horrifying turn. The third roommate came home from work during her lunch hour and noticed something was wrong when Gonzales told her not to go into the bathroom. Later that same day, she returned and detected a metallic smell throughout the apartment.
What happened next would haunt investigators for years. "Shortly thereafter, she heard sawing noises coming from the bathroom, which lasted for four hours," the San Francisco District Attorney's Office reported in an April 2026 press release announcing Gonzales' conviction. "The next morning, Ms. Gonzales was still in the bathroom."
The Investigation
When the third roommate returned home that night, she found the bathroom door open and the apartment filled with the acrid smell of vinegar and bleach. She also noticed a blue container that once held her dirty clothes had gone missing.
"She observed a hacksaw under the sink in the laundry room," prosecutors said.
The roommate asked Gonzales where Mamer had gone. According to investigators, Gonzales offered a chilling response: that Mamer had left "but not the way she wanted to."
Police were called to the residence on June 2, 2018, after a concerned citizen reported what Gonzales had done. Officers discovered large plastic bags stacked inside a maggot-filled container in the home's storage area. Inside were "the rotting remnants" of Mamer, which had been "chopped/sawed up."
Investigators processed the bathroom scene and found blood spatter everywhere. An autopsy later revealed Mamer died from multiple sharp force injuries to her head and heart, including numerous stab wounds to her face and skull.
The Charges
Lisa Gonzales, 55, was convicted by a San Francisco jury of second-degree murder by use of a deadly weapon for killing Mamer in May 2018. Prosecutors presented evidence that before the murder, Gonzales had been offered legal options to evict Mamer through proper channels.
"No thanks, I'll do it my way," she told her co-workers, according to the DA's office.
This week, Gonzales was sentenced to 31 years in state prison for the killing that prosecutors described as "heinous."
Key Takeaways
- Margaret Mamer, 61, was killed by her roommate Lisa Gonzales over a rent dispute in May 2018
- Gonzales used a knife and hacksaw to kill and dismember her roommate before attempting to conceal the body
- A third roommate heard four hours of sawing noises coming from the bathroom on May 15, 2018
- Mamer's remains were found stacked in plastic bags inside a maggot-filled container
- Gonzales was sentenced to 31 years in prison after being convicted of second-degree murder with a deadly weapon
What's Next
The case is now closed following Gonzales' sentencing. While the victim's family and friends waited more than six years for justice, prosecutors said they are grateful for their patience and commitment to seeing the case through.
"This was a deeply disturbing and heartbreaking case," said Assistant District Attorney Melissa Demetral after the conviction was announced earlier this year.