Seniors at Bridgewater Raritan High School have been participating in the elimination game, in which others are eliminated by ski-masked students in surprise water-gun attacks after school and on weekends, police said.
The game is banned from school grounds.
"We are asking parents to please speak to your child about this activity so we can help keep the Bridgewater-Raritan Students and Community safe," authorities said.
"If your child does, in fact, participate in this, please reinforce that under no circumstances should they run or avoid the police, as the police are trying to ensure that no illegal activity is taking place."
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