The 20-year-old man accused of beating his three-year-old stepdaughter to death was charged with assault as new details emerged about the horrifying incident.

Kelsey Smith, 20, was watching his stepchildren, Jeida Torres, 3, and Andrew Torres, 5, on Saturday while their mother was at work. The family was living in an apartment 38 Cooper Street, a city homeless shelter in Brooklyn.

Sources claim that Smith "flew into a rage" when Jeida soiled her diaper. According to the Post, "Andrew told cops. Smith 'pulled the diaper off her and put it in her face and said, ‘Eat it!'' the boy told officers. The little girl refused. 'Then he put the diaper in my face and told me to eat it,' Andrew said, according to sources."

The source said, "Then he kicked her, picked her up and banged her into her crib." Apparently little Andrew tried to defend his sister, but then Smith allegedly beat him as well.

Smith reportedly fled the apartment, but then, the Daily News reports, "call[ed] 911 and posing as a neighbor. 'He was acting as (if) he was some downstairs neighbor and the kids upstairs were acting up. There was absolutely no emotion. He didn’t sound upset at all,' a source said. 'The kids are acting up upstairs,' the source claimed Smith said. 'You gotta send the police.'"

When emergency responders arrived at the apartment at 3:51 p.m., Jeida was unconscious and unresponsive and Andrea had bruises on his body. Jeida was pronounced dead at Wyckoff Hospital.

Smith was found at his aunt's home in Queens, with his wrists slit, in an apparent suicide attempt. Smith's uncle, Mark Almodovar, said his nephew only "backslapped” Jeida, "The kid, he’s not that type of person. They said he was a monster — he’s not a monster. Sometimes kids don’t listen to their parents and they need to be disciplined. But the way he disciplined them was very wrong." Almodovar also claimed that his nephew tried to administer CPR to Jeida, but left when that didn't work.

The investigation is continuing.