"I knew somebody was dead," neighbor Frank Valbiro said.
He heard screaming around 5:00 Sunday morning.
"It was a young girl's voice screaming what you'd scream if something horrible had happened," he said.
Police say around that same time, they got a 911 call from a 14-year-old girl.
"She was pretty much hysterical," Port Chester Police Chief Joseph Krzeminski said.
Krzeminski says the girl's father, 54-year-old Anthony Guglielmo, was found stabbed in the heart in a bedroom into which he had apparently stumbled after being stabbed.
What was weird was the timing. When EMTs arrived they said he'd already been dead for a couple of hours.
"If you were to listen to the tape, which we won't release yet, you would think this just happened. She even describes a man says he is dark skinned with a dark shirt," Krzeminski said.
He said the break-in evidence may have been staged.
Neighbor Alice Quindlen's backyard backs up to the father's house. She heard a loud noise at 3:40.
Other neighbors say father and daughter moved in about a year ago and had a lot of BBQs.
Police say the father had had custody of his daughter since she was 3.
"I used to say hi. Nice. Never heard them fighting or anything," Quindlan said.
"Person of interest? I don't know. If she is a person of interest, I give that 14 year old props. To fake that kind of screaming, scariest thing I've heard in my life," Valbiro said.
The girl, whose name was not made public, had been living with her divorced father. She was released to her mother, who lives in Manhattan.
The chief said no charges have been filed. A kitchen knife and other evidence are being analyzed and an autopsy is planned.