ROCKLIN (CBS13) — A former murder suspect has been set free while investigators determine whether it’s actually a case of self-defense.

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“When the police came to my house in the morning and got him.”

That’s the first time Natalie Kachmar knew something was wrong. Her son, 19-year-old Zachary Kachmar, was under arrest for murder.

“It’s been terrifying hearing the news that somebody in the community has been killed, and my son being involved.”

But Natalie insists her son is no murderer, despite the death of 51-year-old Robert Vickney, who died from a stab wound at his home on Saturday night.

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“This was an accident, this was a tragic accident, and my heart goes out to the victim’s family.”

While the actual circumstances of what happened at the home still remain unclear, investigators say there was a physical altercation between Vickney and Kachmar, and they believe Kachmar stabbed Vickney with a pocket knife.

But on Tuesday, the murder charge was dropped and Kachmar was released, for now.

The Placer County District Attorney’s Office issued a statement that read in part, “The preliminary case includes information that was received by detectives after Kachmar’s arrest that suggests that the suspect may have acted in self defense or without criminal intent.”

While Kachmar’s mother wouldn’t elaborate on what led to Vickney’s death, sources tell CBS13 that Vickney may have become angry with Kachmar. In his mugshot ,there’s an obvious bruise below Kachmar’s throat.

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“This was obviously an accident, but I’m relieved that this is what it’s turning out to be—that it was not intentional, it was an accident.”