Authorities identify the suspect as 29-year-old John Perez of the 4300 block of Glendale Street.
He is charged with murder and related offenses.
The Associated Press reports that Perez was free on bail for a drug arrest at the time of the shooting.
The victim, Jesus Rivera, was an 11th grade student at the Philadelphia Learning Academy.
Rivera was attending a block party in the area of North 5th Street in North Philadelphia following the Puerto Rican Day Parade.
Then, around 12:45 a.m. Monday, witnesses say a fight broke out at 5th and Cambria streets. One of the young men involved in the fight, now identified as Perez, returned with a gun.
Police say he randomly fired several dozen shots into the crowd, killing Rivera, an innocent bystander. Rivera was with his 17-year-old sister who watched him die.
The victim's father, Adrian Zayas, is trying to come to grips with his terrible loss.
"I don't know what to think, I haven't slept or nothing," Zayas said.
Residents say it was a horrible end to what had been a community celebration.
"It's very sad, it's sad in a way, young kids starting to live, it's no words to it," Julio Rosario of Fairhill said.
Rivera was one of five children who live with his parents on Lardner Street in Northeast Philadelphia.
"He was a great kid, he was an honest kid and he was about his business, he was doing what he had to do. He wasn't a bad kid, I understand if you were a bad kid something like that happens to people that's in the streets, but he wasn't that type of person," Zayas said.
Authorities say considering all the bystanders who were out there, it's a surprising no one else was shot.