A fatal shooting in a residential neighborhood in Fremont, which is being characterized as an act of self-defense, sounds like a tragic end to a psychotic episode that was left untreated.

The shooting happened Tuesday around 5:15 p.m. on the 4200 block of Doane Street in Fremont, which is just north of Auto Mall Parkway. The victim, a man in his 30s, had reportedly been threatening and chasing a neighbor who was in his car, and a relative of that neighbor, who was also allegedly threatened by the victim, is the suspected shooter.

The neighbor who was harassed while in his car explained to KPIX, "He punched my window, and I rolled my window down … The first thing he told me – I’m gonna kill you. And then he was chasing my car, running like a crazy man chasing my car. And at that time I got really scared I think maybe he has a gun and he would shoot me or something because he kept chasing me. And after that I drove away and called 911 right away."

When this neighbor circled back to his home, he says, his elderly stepfather who had been watching the confrontation from outside their home was standing there, and the victim was also there, fatally shot.

Karthik Manivannan, the victim's second cousin, tells KTVU that the victim had been having some sort of mental health episode recently. "He's not aggressive, but you never know how other people are going to take it. But he was never aggressive to anyone. He would talk nonsense, but he was never aggressive towards anyone."

But, Manivannan also told NBC Bay Area that the family had recently called police twice as his cousin was experiencing these episodes, but police did not detain him or have him committed. The family also says they reached out to a regional mental health services center.

"Cops came out twice. Both times they said he was not aggressive; he doesn’t qualify as a threat and they went back on both occasions,” Manivannan tells NBC Bay Area. "We tried really hard to get him mental services."

Manivannan added, to KPIX, "The system and the cops kept telling us the best we could do is wait."

The stepson of the suspect, who said the victim threatened to kill him, told KTVU that the suspect "attacked" his stepfather before the shooting took place.

The investigation is ongoing, and neither the suspect nor the victim have yet been publicly identified. The victim is said to be in his 30s.

Lt. Ricardo Cortes of the Fremont Police Department told KPIX Tuesday night, "We have a lot to work. Detectives have been called out and have taken over this investigation and they will be working probably all night determining what actually happened."

We'll update you as we learn more.

Photo: Getty Images