Maurice Stephon Phillips is facing multiple charges including 3rd-degree murder, involuntary manslaughter and other offenses.
The man turned himself into police late Saturday night.
Police say following their investigation, the man admitted to the shooting.
He told police the 5-year-old sibling had nothing to do with it.
Police say the man is a father to one child and a stepfather to another.
PHOTOS: Fatal shooting inside Kensington home
Despite the alleged confession, as a small memorial grows outside the family's home, so does confusion over who pulled the trigger.
"Everybody's hearing different stories, and nobody knows what the truth is. Only what happened," said neighbor Rachel Santana.
Santana tells Action News she comforted the mother of the 4-year-old moments after the child was shot and killed.
"She was basically in shock," said Santana. "She kept saying, 'My baby, my baby,' and 'Oh my God, how'd that happen? I don't understand. My baby.' "
UPDATE: Medical examiner just arrived at scene of shooting death of 4yo in Kensington. pic.twitter.com/kfa0DSVSiw— Jeff Chirico (@JeffChirico) April 16, 2016
Santana says she's friends with the mom, but doesn't know much about the dad. She says she isn't surprised to hear people in the neighborhood would keep a weapon in their home.
"Some people know that it's wrong, but we live in such a bad society, especially here. It's really bad around here.
"People feel that they need to protect themselves at all costs, and it was just a tragic accident that happened," said Santana.
Neighbors tell us the mother suffered a seizure Saturday night, and was taken to the hospital.
The shooting happened just before 2:30 p.m. Saturday along the 200 block of East Mayfield Street.
Police say the child was shot once in the chest, and was pronounced dead at the scene.
Homicide detectives spent hours inside the home trying to piece together what led to the shooting.
Police say the little girl lived in the home with her mom, dad and six siblings.
The neighbors say the mom was very protective of her children, and she would only let them play in the backyard because she was afraid of the crime on the street.
"I said why don't you bring the kids out?" said neighbor Louise Sawyer, who tells us the mother's response was, " 'No I'm not bringing these kids out here with all this trouble.' "
"She was a sweet, loving, little girl," said family friend Crystal Dougherty. "She was full of life. She was always willing to help. She was a great big sister to her little brother."