San Jose police officers who fatally shot man after he killed young son cleared of wrongdoing

Two San Jose police officers acted lawfully when they shot and killed a man who had fatally stabbed his young son last year, the Santa Clara County District Attorney's Office said.

The DA's Office issued a report on Wednesday on the fatal police shooting on July 13, 2025 at Cataldi Park in East San Jose, which concluded that lethal force used was justified and reasonable under the circumstances.

Officers had responded at about 3:30 p.m. to a 911 call from 48-year-old Fremont resident Mateusz Dzierbun, who reported that his 9-year-old son had been stabbed to death by another person. The San Jose Police Department said he later admitted to dispatchers that he did it, saying, "They were going to torture him ... I had to do it."

Officers arrived to find Dzierbun holding a butcher knife and kneeling next to the child who appeared to be severely injured and bleeding. Police said officers warned Dzierbun numerous times to drop the knife so they could attend to his child, but he would not comply. According the report, Dzierbun told officers: "If you get the stun bag, I'm going to get up and charge this guy."

"The officers were confronted with an extraordinarily dangerous and rapidly evolving situation," the report stated. "The evidence before them indicated only two possibilities: either Dzierbun had already murdered his son, demonstrating his homicidal intent, or the child had been stabbed by Dzierbun and required immediate lifesaving aid."

The report said Dzierbun made multiple comments indicating an intent to provoke a lethal response from the officers.

The officers again stated, "Sir, will you please drop the knife?" Dzierbun responded, "Listen to me very carefully. I am armed, and one of you guys is going to kill me today. I don't want to traumatize you." The officer repeated for a third time, "Sir, I need you to drop the knife," to which Dzierbun responded, "I don't want to traumatize anyone here ... so listen to me carefully, whoever killed someone before needs to be here."  

Police body camera footage showed that within two minutes of the officers arriving, Dzierbun stood up, brandished the knife above his head, and charged at the officers. Sergeant Joel Casey and Officer Eduardo Eyer opened fire, hitting Dzierbun 14 times.

The District Attorney's Office said by law, officers can use deadly force when they or others face imminent danger.  

"Officer Eyer and Sergeant Casey were less than 30 feet away from an individual charging at them armed with a knife," the report concluded. "The facts before them clearly support their belief in the necessity to use lethal force to prevent death or great bodily injury to themselves or their fellow officers"

At the time of the killing, Police Chief Paul Joseph said that in his more than 30 years of service with the San Jose Police Department, he's never seen anything comparable.

"The child suffered from injuries so severe that it's unimaginable they could have been inflicted by his own father," Joseph said.

Dzierbun had no criminal or mental health record in Alameda or Santa Clara counties, but police said that he had moved throughout the country.