SAN FRANCISCO (CBS SF) — Police in San Francisco responded when shots rang out near the U.N. Plaza. It happened around 6 p.m., during crowded gay pride Pink Saturday celebrations.

The incident was caught on cell phone video and shared widely on Instagram.

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Police said the altercation was between two groups of teenagers. Six of them have been detained. It is still not certain whether the clash was gang-related.

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A vendor at one of the Pride booths was wounded and taken to the hospital. Police said they are expected to survive.

The cellphone video reveals at least four shots were fired. Screams are heard. Then, the video breaks up as spectators disperse.

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Police said the Pride event was about to shut down when the shooting occurred.