Authorities have not yet commented on what they believe happened on Thursday afternoon. They believe that autopsy will provide some answers.
"There was a pellet recovered that was a different caliber than the gun that was found in the house, so we just don't know what gun was used during the shooting," said Police Commissioner Charles Ramsey.
Police said on Friday morning that they have recovered a gun, but did not yet know if it was the gun involved in the shooting.
"I miss my grandson, I miss him," the boy's grandfather Edgar Perez said. "My grandson's gone, my grandson was a kid. He didn't mess with nobody. He's 4 years old, what's a 4-year-old gonna do? Nothing."
Police say shortly after 4:30 p.m. Thursday they received a call about a child bleeding from the head inside a home in the 600 block of East Clementine Street.
"They found a 4-year-old bleeding from the head. The fire department paramedics transported the child to St. Christopher's Hospital. They worked on him, but the child unfortunately was pronounced at 5:07 p.m.," Philadelphia Police Chief Inspector Scott Small said.
Police say the Javier's father and mother along with others were in the home when the shooting happened.
Javier's grandfather was blaming the boy's father for leaving a gun out in the open where a child could reach it.
"I'm hurt, I'm hurt a lot cause he was only 4 years old, How are you going to play with guns? I see him playing with plastic guns, but with a real gun? Come on," Perez said.
Homicide investigators continue to interview witnesses, but so far, no one has been charged with a crime.
Meanwhile Javier's cousin, Marcus, helped build a memorial outside the Kensington home.
"He's a kid, nothing to do with anything. Innocent kid, loved to play. He had autism but you couldn't tell. He was smarter than anybody," Marcus said.
Neighbors brought teddy bears, lit candles, and prayed while messages were written out to young Javier on his front door. The community was mourning the death of the friendly boy who loved bikes and video games and dressed up as Batman for Halloween.