MORGAN HILL, CA – Authorities have charged a 20-year-old Morgan Hill man with murder after his girlfriend was found dead near a local lake, following a confrontation over her alleged communication with an ex-boyfriend.
Martin Mendoza Jr., 20, stands accused of killing Marissa DiNapoli, 18, whose body was discovered at Anderson Lake on July 2. Investigators say Mendoza stabbed DiNapoli multiple times in the back and left her to die after an argument escalated the morning of June 29.
Surveillance footage from a residential Ring camera captured Mendoza and DiNapoli leaving a home together shortly before 10 a.m. that day. According to the Santa Clara County District Attorney’s Office, DiNapoli appeared visibly anxious as the two departed. Cellphone tracking data later placed both individuals near Anderson Lake within minutes of their departure.
Data further shows that both Mendoza’s and DiNapoli’s phones arrived at Anderson Lake between 9:58 and 10:04 a.m. Roughly ten minutes later, their phones tracked west on E. Dunne Avenue. At 10:18 a.m., video surveillance recorded Mendoza’s vehicle heading toward Highway 101, while DiNapoli’s phone registered its final activity.
Family members and coworkers were quick to report DiNapoli missing after she failed to arrive for a shift at a local Starbucks, which they said was uncharacteristic for the reliable teen. Concern intensified as investigators uncovered evidence suggesting the couple’s relationship had been marred by previous, unreported incidents of domestic violence.
On July 1, authorities detected Mendoza’s vehicle crossing into Mexico at the San Ysidro border checkpoint. DiNapoli’s body was found a day later, bearing five stab wounds to her back. Mendoza was arrested while attempting to re-enter the United States on July 6.
Prosecutors charged Mendoza Tuesday with murder, citing aggravating factors including use of a deadly weapon, infliction of great bodily injury, taking advantage of a position of trust, and allegedly targeting a vulnerable victim. The defendant was denied bond during arraignment and did not enter a plea.
Law enforcement officials say the investigation drew on multiple sources, including surveillance footage, cellphone data, and interviews with those close to DiNapoli, to reconstruct the events leading to her death.
Mendoza remains in custody as authorities continue building the case. They emphasize the importance of reporting domestic violence, noting that several violent incidents between the two had gone unreported prior to the killing.