CHICAGO (CBS) — A Chicago activist who spends a lot of time on the streets trying to prevent violence is warning about people who target trick-or-treaters and their parents with paintball guns on Halloween.

Community activist Andrew Holmes said the people who fire paintball guns at trick-or-treaters think it’s funny, but the victims often end up in the hospital, because of injuries.

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“They think it’s funny. They see them duck, they see them fall, they see them crying, them hollering, and they’re filming it. They think it’s a joke. It’s not a joke, this is very serious,” he said.

WBBM Newsradio’s Mike Krauser reports Holmes demonstrated how a paintball gun uses high levels of air pressure to fire paint-filled pellets, which can cause serious eye and ear injuries.

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At virtually any paintball course, players must wear protective goggles and masks, and are prohibited from aiming at anyone’s head or face. Many courses also require paintball players to wear protective vests, or other padding.

Holmes warned anyone thinking of shooting someone with a paintball gun as a prank that they could be liable in a civil lawsuit if they hurt someone.

He said parents should keep an eye out while taking kids trick-or-treating on Halloween, to help avoid any trouble.

“Look around, check your surroundings; every car, and every person that’s walking, every person that’s standing in a gangway. Look at them, and look at them real tough,” he said.

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Holmes said he and other community activists monitor YouTube and Facebook for videos of people firing paintballs as pranks, in an effort to identify them in cases where someone is hurt.