(CNN) Over the weekend, thousands of people flocked to a popular music event in Brooklyn and on the other side of the country, thousands more to a food festival in Northern California.

But even though the festivals were on opposite coasts, the experience of revelers was eerily similar: The family-friendly events soon turned into nightmares.

In New York, one man died and 11 others were injured by gunfire Saturday night, police said.

In Gilroy, California, crowds trampled over each other on Sunday trying to escape a shooter that sneaked into the city's annual food festival by cutting a hole in a fence. Three people -- including a 6-year-old boy -- were killed. Twelve others were injured.

Both tragedies caught unsuspecting crowds by surprise as they enjoyed time with family and live entertainment.

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