A 20-year-old man has been charged in the beating death of his 3-year-old stepdaughter after the child was found bruised an unconscious at a Brooklyn homeless shelter near her injured 5-year-old brother, police say.

Jeida Torres was discovered unconscious and unresponsive Saturday afternoon in a homeless shelter on Cooper Street in Bushwick, police said.

She was taken to a hospital in cardiac arrest and was pronounced dead. Her brother was in stable condition at Wyckoff Heights Medical Center.

Neighbor Keith Best told the Daily News and New York Post that the boy had big bruises on his face and arms. He said the children's mother and grandfather sobbed when they arrived home and found out what had happened.

Police have arrested 20-year-old Kelsey Smith in connection to the girl's death, and charged him with assault and acting in a manner injurious to a child, the NYPD said. The man cut himself in a suicide attempt before his arrest, and he was brought to the hospital in stable condition, police said.

Police say that Smith was watching Torres and her brother while their mother was at work. The beating may have stemmed from the 3-year-old soiling her pants.

Smith has 15 prior arrests, including one for assault. It's not clear if he has an attorney.

Mark Almodovar identified Smith as his nephew and the children's stepfather.

Almodovar said he believed his nephew had struck the girl. But Smith is not a monster, Almodovar insisted, adding that the younger man had to help Jeida after she was injured, giving the child chest compressions.

"She's on the floor and she's not moving so he tried to give her chest compressions," Almodovar. "When he gave her chest compressions he partly made her stop breathing, so he left the house."

Camille Rivera, deputy commissioner for the Department of Homeless Services, said the agency was helping investigators.

"The death of a child is a tragic incident which we are taking extremely seriously. We are working with the NYPD to determine how this occurred," she said in a statement.

--Katherine Creag and Lori Bordonaro contributed to this report.