Jonathan Thompson, 31, was charged with second-degree murder in the death of the youngster, Adonis Reed, who was found unconscious on a couch in an Amityville apartment on Wednesday afternoon.
At Thompson's arraignment in Central Islip, prosecutors said he struck the boy hard enough to lacerate his liver. They said he had been babysitting for the child for his primary caregiver, a godmother, and told investigators he became angry when the boy wouldn't go to sleep.
Dozens of relatives of the slain boy attended Saturday's court session. Some screamed and swore in the hallways after the proceeding, calling Thompson a "baby killer."
An aunt of the boy, Lashon Reed, called the child "a God-given gift."
"He was wonderful. He was the love of our lives and he never hurt anybody. I just don't know what to say," she said.
Thompson's lawyer, Joseph Hanshe, asked a judge to issue a protective order because his client had been threatened after his arrest, but that request was turned down.
The boy's sister was in the custody of county child welfare officials, police said.
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