The crowd runs away from gun shots at Civic Center Park after the 4/20 pot rally, Saturday, April 20, 2013 in Denver. Gunfire erupted at a Denver pot celebration Saturday, injuring two people and scattering a crowd of thousands who had gathered for the first 4/20 counterculture holiday since the state legalized marijuana. Denver Paramedics, Denver Police officers and good Samaritans tend to a shooting victim at Civic Center Park after the 4/20 pot rally, Saturday, April 20, 2013 in Denver. People hide and run away from the gun shots at Civic Center Park after the 4/20 pot rally, Saturday, April 20, 2013 in Denver. DENVER (AP) - Denver police urged the public to view a YouTube video Monday that may help them identify an accomplice in a weekend shooting at a marijuana celebration that wounded two people and scattered a crowd of thousands. Police spokesman Sonny Jackson said the man is shown walking away from the shooting scene as sirens wail in the background. The suspect is a black male wearing a brown and white checkered shirt. He can be seen about six seconds into the video, Jackson said. "We are seeking this individual as we believe he assisted the primary suspect after the shooting," Jackson said in a prepared statement. A primary, unidentified suspect in the shooting was wearing a blue hat, grey sweatshirt and black pants, Jackson said. Saturday's shooting happened at the end of an outdoor celebration of the first 4/20 counterculture holiday since Colorado legalized marijuana. A man and a woman suffered non-life threatening gunshot wounds. A juvenile grazed by a bullet was treated at a nearby hospital, police said. The police gang unit has taken over the investigation, although it isn't yet clear if gangs were involved, Jackson said. As was the case in the Boston Marathon bombing investigation, Denver police asked those at the rally to share anything they may have seen, photographed or recorded at the event. When gunfire happens people run away. Now that things have calmed down, we would like them to come back and talk to us," Jackson said. The jovial scene at the downtown Civic Center Park turned to panic when the shots were heard. Several thought firecrackers were being set off, then saw a man bleeding. YouTube video: Information from: The Denver Post, http://www.denverpost.com