Bryant's daughter and seven others were also among the dead.
"We lost one of the greats. The Mount Rushmore of basketball," said Romeire Brown of Wynnewood.
Kobe played ball at Lower Merion from 1992 to 1996 and went directly to the NBA.
People were bringing flowers, basketballs and jerseys as a memorial began to grow outside the school.
"The Lower Merion School District Community is deeply saddened to learn of the sudden passing of one of our most illustrious alumni, Mr Bryant. Mr Bryant's connection to Lower Merion, where he played basketball before joining the NBA, has raised the profile of our high school and district throughout the world," said school district spokeswoman Amy Buckman.
Chris Palmieri of Newtown Square said Bryant was a big part of his childhood.
"He was what I watched, what I studied. He taught me how to play, how to compete, how to win, how to lose," said Palmieri.
Throughout the evening, the memorial grew. Mourners stood silent in tribute.
"It's absolutely tragic. We were playing (intramural basketball) and the commissioner stopped the game and said that Kobe Bryant passed away. It was a shock to everybody," said Josh Axelrod, a student at Lower Merion High School.
Mike Rinaldi, a student at nearby Harriton High School, said he recalls stories his father told about playing with Bryant.
"Kobe would make him the most driven man in the court. You always wanted to guard Kobe because he was the best out there. Kobe made him a better player," said Rinaldi.
The best at the game didn't forget where he came from.
Marisa Miller of Roxborough admired Bryant for his philanthropic missions.
"He was so influential on the youth, making sure they had athletic skills, academic skills, opening these schools, giving back," said Miller.
In a statement, Bryant's former coach at Lower Merion Gregg Downer said, "Aces Nation has lost its heartbeat."