SAN FRANCISCO (CBS SF) — Disturbing incidents with creepy clowns are occurring across the nation.

According authorities, people dressed in clown costumes have been at the center of dozens of hoaxes in 23 states.

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The pranks range from mild to violent, even fatal.

Victims reported being chased, threatened, and harassed. In Pennsylvania, a teenager was fatally stabbed by a prowler wearing a clown mask.

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There have been 12 arrests nationwide, according to the New York Times.

The clown crimes have authorities scratching their heads for a motive. Some believe these creepy clown incidents will increase as Halloween approaches.

California experienced a spate of similar incidents back in 2014, when several evil-looking clowns were sighted roaming the streets of Bakersfield.

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The trend has spread to some 23 states. Since the end of summer, there have been incidents involving people dressed up as clowns reported in Alabama, Arizona, Arkansas, Colorado, Florida, Georgia, Idaho, Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, Missouri, Mississippi, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, Washington, West Virginia, and Wisconsin.