TOMS RIVER, N.J. -- Brittany Cena's mother reported her daughter missing around 4:30 p.m. Tuesday.

But the family soon learned the teen's body had been in the basement of her home the whole time after authorities said she was choked to death by her own cousin.

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NBC 10's Ted Greenberg reported that Garry Zigich Jr., moments after he walked into court Wednesday, appeared to express a message of remorse to grieving family members, mouthing the words, "I'm sorry. I didn't mean it."

"It's sad, it's just scary," said former neighbor Lucy DiMicco.

A small memorial now sits outside the home where prosecutors believe Zigich strangled his 15-year-old cousin with his hands Tuesday morning. The girl's grandfather found her body that afternoon under a blanket in the basement -- the same area where Zigich had been sleeping for the past month.

"I knew Brittany since she was 8-years-old, and I used to take her to church with me. She was a sweet girl," DiMicco said.

"She was just a nice person," said another of Cema's friends.

Authorities said the high school sophomore was killed sometime between 6:30 a.m., when she talked with a friend on the phone, and 9 a.m. That's when Zigich checked himself into a Monmouth County Hospital. Police arrested him there Tuesday night.

"He had asked to be admitted there. He was complaining of suicidal tendencies, I believe," Ocean County Prosecutor Marlene Lynch Ford said.

"Do you understand that?" a judge asked Zigich during his arraignment Wednesday.

"Yes," he answered.

Investigators would not comment on a possible motive but said they knew of no prior problems between Zigich and his cousin.

"You can't trust people, nowadays. It's a shame," DiMicco said.

Grief counselors were on hand at Cena's school, Toms River High School North, on Wednesday.

Zigich is locked up in the Ocean County Jail. His bail set at $500,000.