SAN JOSE — Police shot and killed a man who viciously stabbed his 9-year-old son Sunday afternoon, after he called 911 to summon officers and then attacked them, leaving the father and child both dead in a tranquil North San Jose neighborhood park, authorities said.

San Jose Police Chief Paul Joseph said that an initial investigation found strong evidence suggesting Mateusz Dzierbun, a 48-year-old Fremont resident, wanted police to shoot him after killing his son. But the chief also said Dzierbun had no criminal history or prior police contact in Santa Clara County or in Alameda County, where he resided, and was not the subject of any child-welfare actions in either county.

At a Monday news conference, Joseph said the two policemen who shot Dzierbun were a sergeant with 19 years with San Jose police and an officer with 4 1/2 years of service with the department. They were on patrol around the Berryessa neighborhood when they were dispatched to nearby Cataldi Park, after a “hysterical” man called 911 to report his 9-year-old son was being stabbed by an unknown attacker.

“These officers had no idea the frantic person on the phone was, in fact, the suspect himself, the deranged man who had murdered his own son, whose call for help was actually a twisted plan to force officers to shoot him, a final desperate and selfish act,” Joseph said.

The chief added: “Officers would later discover that the 9-year-old child they were rushing to save was already deceased … from injuries so severe that it’s unimaginable (they) could have been inflicted by his own father.”

In the three minutes between when officers arrived at the park and when they opened fire, Joseph said the officers repeatedly ordered Dzierbun to drop the large bloody knife he was holding and allow them to provide medical aid to the boy.

“Officers realized they could not continue to plead for cooperation with the suspect any longer if they needed to reach the child,” he said. “The suspect unexpectedly stood up with the knife raised and charged at the officers. The officers discharged their firearms, striking him.”

Both officers who shot at Dzierbun were crisis trained and had their body-worn cameras activated. Under state law, the police department has to release footage from the shooting within 45 days. A third officer deployed his Taser at the same time the other officers opened fire.

“The officers who responded that afternoon were running toward what they believed was a child desperately in need of help. They came intending to save a life, not take one,” Joseph said. “They had no way of knowing this horrific and unfathomable act of violence had already led to the loss of an innocent child’s life.”

Sunday’s incident marked the city’s second fatal police shooting in a week. On July 6, police shot and killed a 37-year-old man who police say shot at officers during a family disturbance call brought on by a psychiatric emergency.

Three police shootings have been recorded in San Jose this year, two being fatal. The stabbing of the child was the city’s 13th homicide of the year.

The shooting also marked a major policy shift by police that effectively denies the Office of the Independent Police Auditor access to police shooting scenes, by removing Internal Affairs investigators from the scenes. That marks a drastic departure from decades of practice, and takes San Jose police out of step from most comparably sized departments.

Previously, either the IPA or a staff member would go out to police shooting scenes and get a briefing from Internal Affairs personnel — who served as liaisons for the auditor’s office — but would be prohibited from getting a close look at the investigation.

That was standard practice for several years, but last month police auditor Eddie Aubrey, both in his office’s annual report and to the City Council, recommended that he and his staff get increased access at police shooting scenes, including the ability to observe officer interviews and body-camera footage, and allowance for a walkthrough at a shooting site.

The police department, backed by the City Council, opposed the request by arguing that a police shooting scene was part of a criminal investigation and required corresponding information restrictions. Aubrey argued that he wanted the same passive on-scene access as Internal Affairs investigators, but the request was ultimately voted down.

On Monday, Aubrey stated on the IPA website that his office was informed on Sunday that Internal Affairs investigators would no longer respond to police shootings, effectively barring his office’s access since they no longer have an on-scene liaison, and are prohibited from interfering with criminal investigators.

“While the shift affects Internal Affairs’ procedures, it does not alter the IPA’s existing protocol or commitment to independent oversight and transparency,” Aubrey wrote. “The IPA Office remains dedicated to strengthening accountability and trust between the community and the San José Police Department.”

At Monday’s news conference, Joseph addressed only the removal of Internal Affairs personnel from police shooting scenes, not the downstream effect it would have on IPA access.

“The rationale is they’re not part of the criminal investigation and they don’t need to be there. It’s probably a carryover from something that’s just been done for many years,” Joseph said. “The IPA pointed out a contradiction for us, and so we took it and made a correction.”

Aubrey, who was present at the news conference, declined to address the chief’s comments when asked about his recommendation’s apparent purpose to expand access for his office, not revoke access for Internal Affairs.

Anyone with information about the Sunday stabbing or police shooting can contact the San Jose police homicide unit at 408-277-5283, or email Detective Sgt. Rafael Varela at 3638@ sanjoseca.gov or Detective Jose Montoya at 3644@sanjoseca.gov.

Staff writers Jason Mastrodonato and Rick Hurd contributed to this report.