San Jose man charged in fatal shooting of girlfriend at Fourth of July party

SAN JOSE — A man has been charged with murder after police say he recklessly opened fire at his girlfriend at a Fourth of July party, killing her in full view of other partygoers.

Diego Ulisses Diaz, 25, of San Jose, was charged Wednesday in the July 5 death of 32-year-old Joselyn Martinez, according to a criminal complaint filed in Santa Clara County Superior Court by the District Attorney’s Office. Martinez has not been formally identified by the county coroner’s office, but she was named in charging documents.

Diaz, who was scheduled to be arraigned Wednesday afternoon, was also charged with two counts of assault with a firearm after police determined he twice fired on Martinez, with the second round of gunshots fatally wounding her and nearly hitting her friend.

Prosecutors also filed charges against Diaz for being a felon in possession of a firearm, and for vandalism after he reportedly kicked open the door and window of a police vehicle when he was arrested within an hour of the shooting.

San Jose police officers were called around 1:20 a.m. Sunday to the area of Bonita Avenue and Sunny Court, near Bonita Park, for a report of a shooting. They arrived to find Martinez suffering from gunshot injuries, and she later died at a local hospital.

According to a probable cause affidavit written by San Jose police detectives, Diaz was quickly identified as the shooting suspect and was recorded on surveillance cameras in the area running along Sunny Court and then on a walkway that led to his apartment on East William Court on the other side of the block.

A nearby resident saw Diaz and another man walking by, and heard Diaz say, “I just shot my girl,” according to the affidavit.

Around 2:05 a.m., about 45 minutes after the shootings were reported, police officers trailed Diaz as he rode in a car from his apartment toward East San Antonio Street and stopped the vehicle.

“During his detainment, Suspect Diaz became verbally and physically agitated and kicked open the rear door and window of a patrol vehicle, damaging it,” the affidavit reads.

Officers reported finding a live 9mm round that appeared to have fallen from Diaz’s body or clothing when they later removed him from the police SUV.

Investigators determined that earlier in the evening, Diaz and the victims were attending a party at or near the park and that Diaz had been bragging about having a new gun, and fired it once into the air. Later in the night, Diaz and Martinez were seen agitated and pushing and shoving each other, followed by Martinez trying to strike at Diaz as they sat in an SUV, according to the affidavit.

Diaz reportedly responded by racking his handgun and firing at Martinez’s feet. A woman friend of Martinez then grabbed her so they could both leave the party, and the friend reported that moments later, she heard three to four gunshots, then fell to the ground as Martinez became “lifeless,” the affidavit states. The friend later told police that she was nearly hit in the head and leg by the bullets.

According to a family GoFundMe fundraising page, Martinez, who public records indicate lived in Salinas, was a mother of five young children.

“It is with heavy hearts that we share the loss of our beloved Jocelyn, a devoted mother, sister, aunt, and daughter,” the page reads, using a variation of her first name. “Jocelyn’s greatest love was her five young children, and now, in the wake of this unimaginable loss, they need us more than ever.”

The Sunday shooting marked the city’s 14th homicide of the year investigated by San Jose police. At the time of the shooting, Diaz was prohibited from possessing firearms after a 2022 felony conviction for unlawfully taking a vehicle.

Anyone with information for investigators can contact the SJPD homicide unit at 408-277-5283 or email Detective Sgt. John Van Den Broeck at [email protected] or Detective Amanda Estantino at [email protected]. Tips can also be left with Silicon Valley Crime Stoppers at 408-947-7867 or siliconvalleycrimestoppers.org.

This is a developing story. Check back for updates.