It happened around 12:45 a.m. in the 500 block of West Cambria Street. Dozens of shell casings littered the street and bullet holes marked car windshields and doors.
Philadelphia Police say they are closing in on the suspect who killed the 16-year-old boy in front of his sister.
It started with the festive celebration of Puerto Rican Day. After the parade, revelers traditionally return to the neighborhoods around North 5th Street for a huge block party.
Then, witnesses say, a fight broke out at 5th and Cambria. One of the young men involved in the fight returned with a gun.
Police say he shot randomly into the crowd and killed an innocent bystander. 16-year-old Jesus Rivera was hit in the arm and chest.
He was with his 17-year-old sister who watched him die.
Rivera is one of five children and lived with his mother on Lardner Street in Northeast Philadelphia.
Police sources say the shooter is a young man in his early 20's, and they know who he is. They are in the process of getting an arrest warrant.