NEW YORK (CBS 2) — What pushed a father to wield a knife against his own family? As CBS 2’s Kathryn Brown reports, a stunned Staten Island neighborhood was searching for answers Monday.

No one knows what sent 41-year-old Douglas Nemeth over the edge, but the man neighbors describe as quiet and happy simply snapped Sunday night.

Police said he lashed out at his girlfriend, 34-year-old Victoria Orlik, and the couples two toddlers, slashing all of their throats before slitting his own.

“We were shocked. We couldn’t sleep last night just thinking about it,” said neighbor Norma McCarthey.

Just before 8 p.m., neighbors heard panicked screams coming from the street.

“I ran out and poor woman holding her neck, screaming, yelling to get her baby, get her baby, get her baby,” said neighbor Kim Avena.

Orlik had their 18-month-old son, Brandon, in her arms, but her 3-year-old daughter, Sasha, was still inside.

Nemeth kept police at bay for nearly half an hour, but after a tense standoff, SWAT teams stormed inside and found Sasha in a bedroom and Nemeth in the kitchen.

Both their throats had been cut.

The entire family was rushed to Staten Island University Hospital where Nemeth was pronounced dead. “What can be in mind you know when something happens like this,” said neighbor Sergei Batov.

Neighbors said Nemeth was an out-of-work chiropractor and stayed home with the kids while Orlik worked as a teacher.

While the couple never spoke of financial strain, some wonder if it played a role in his violent rage.

“I don’t know. He had to have, you know, lost it. Literally lost it,” neighbor Kim Avena sighed.

Friends and relatives can now only pray pray his family survives the rampage. The mother and two children were listed in critical condition.

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