Columbine High School students Eric Harris and Dylan Klebold entered the suburban Denver school, slicing the air with bullets, killing 12 classmates and a teacher and injuring 23 others before committing suicide.
Columbine Principal Frank DeAngelis attended the school's prom last weekend when two students with special needs were crowned king and queen, an act he said exemplifies the school's true spirit, CNN reported.
"This," DeAngelis told KMGH-TV, Denver, "is what Columbine is all about."
Colorado Avalanche winger Milan Hejduk, a rookie in the National Hockey League when the massacre occurred, called the shootings "a brutal thing," the Denver Post reported.
"We'll all remember it forever," Hejduk said.
Eleven years ago, the San Jose Sharks and Avalanche were scheduled to open a first-round Western Conference playoff series the night after the shootings.
Current Sharks star forward Patrick Marleau, in his sophomore NHL season in 1999, recalled his incredulity when learning what happened.
"There were police cars and ambulances scrambling, and at that time, we didn't know the extent of what was happening," he told the Post. "I was a couple of years out of high school, but I think everyone was in disbelief because of what happened."
After discussions among the teams and NHL officials, the series was rearranged, with Games 1 and 2 switched to San Jose on April 24 and 26.
"I remember the moments of silence for the victims before each game and what a tough time it was for all of Colorado and around the country," Marleau said.