Shots were fired into a crowd celebrating the marijuana holiday 4/20 Saturday in Denver.
Three people were injured and tens of thousands fled as shots rang out at 5pm, just after the crowd shared joints for a massive, 4:20pm smokeout.
A man and woman, both between 20 and 30 years old, were shot in the leg, and a juvenile was grazed by a bullet, ABC 7 News in Denver reported.
The organizer of Denver's 4/20 rally told ABC 7 News that this was the first time there's ever been a shooting in the 29 years the gathering has taken place.
Saturday's 4/20 holiday was the first public party since marijuana was legalized in Colorado and Washington last year.
Police spokesman Sonny Jackson told Fox News that two people, a man and a woman, were taken to a hospital with gunshot injuries that did not appear to be life-threatening.
Witnesses described screaming and panic as gunshots rang out through the celebration.
One witness, Travis Craig, told AP that he thought the noise was firecrackers but then a man fall down bleeding.
"I saw him fall, grabbing his leg," said Craig, 28, who told AP that he used a belt to apply a tourniquet to the man's leg.
"He was just screaming that he was in pain, and wanted to know where his girlfriend was. She was OK. And then the cops showed up real quick, like, less than a minute. They put him on ambulance and left."
After the shooting, all 4/20 pot-related events at Civic Center Park scheduled for the rest of the weekend were cancelled.
The 4/20 party was expected to draw a crowd of 80,000 in the park beside the state Capitol.
The Denver Police Department's Gang Unit has taken over the investigation, according to ABC News 7. Investigators are requesting anyone with video footage from the rally to contribute it to the investigation.