SAN JOSE, Calif. – A witness who saw San Jose police officers shoot and kill a man in a city park says – two days later – he remains traumatized.  Police later revealed the man they shot on Sunday had just killed his 9-year-old son in the park and then called police himself. 

The absolute shock of this crime is apparent with everyone involved, from veteran police officers to witnesses to city leaders.  

“You can’t even put it into words,” said James Testa, who witnessed the incident on Sunday afternoon. 

Testa had just finished a basketball camp he teaches and was on the nearby pickleball courts at Cataldi Park when he saw police officers responding. A small memorial now stands in the park near where the incident occurred.

“A police officer can go his whole working career and not see something like this. A citizen, myself, witnessing and just seeing a 9-year-old boy and then the police shoot the father. It was a sad day – to see two people die. Very sad,” Testa said. 

At the time, Testa did not know that the boy he saw on the ground was the son of the man in the confrontation with police.  Testa has two kids of his own —including a 7-year-old. San Jose police later identified the suspect as 48-year-old Mateusz Dzierbun of Fremont. 

“My heart does feel heavy, it hurts. It is like having a burden on your heart just for a lot of reasons – just being a witness of a young boy but also the way the police shot the man,” Testa said.

In a news conference on Monday, San Jose Police Chief Paul Joseph revealed the officers who responded to the call thought they were there to help a child being attacked.  

But, Joseph said, it was the suspect himself who was on the line requesting police in a likely suicide-by-cop situation.  

“Before a less lethal option could be deployed, the suspect unexpectedly stood up with the knife raised and charged at the officers,” Joseph said. 

San Jose City Council Member David Cohen represents the ares where the park is located.

“This is a vibrant community park that people are enjoying in the middle of a Sunday afternoon,” he said.

Cohen said this appears to be a case of very public domestic violence and not related to the safety of the park itself.  

“As a parent all of us – those of us who have kids and even those of us who don’t – are in shock about the idea that somebody could behave this way,” Cohen said. 

San Jose Mayor Matt Mahan also released a statement on this case.

“There are no words to describe how horrific and heartbreaking this act of violence is,” Mahan said. 

This incident is being investigated as the 13th homicide of 2025 according to San Jose police. 

San Jose Police shooting takes tragic twist | Take 2 Nightly

KTVU’s anchors discuss the latest developments in a story out of San Jose where police shot and killed a man wielding a knife over the weekend. Today we learned the man who police shot and killed was the 911 caller and that he had just stabbed his son to death before police arrived. Officials say he was trying to lure police to the scene to and had made several statements that he wanted them to shoot him.