EAST ISLIP, N.Y. (CBSNewYork/AP) — Animal cruelty investigators are looking into what they believe is the fourth ritualistic animal killing on Long Island in a month.

Suffolk County SPCA Chief Roy Gross said Friday that investigators believe the incidents are the result of religious rituals.

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He said an 18-inch cow tongue was found nailed to a tree in an East Islip park Thursday morning. It was wrapped in fabric.

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Gross believes the ritual is typically meant to stop rumors or stop someone from testifying in a court case. He said detectives are looking into the possibility that gang members are responsible.

Another cow’s tongue was found affixed to a tree nearby earlier this month. Three goats were also found dead in June.

A $2,000 reward is being offered for information leading to an arrest.

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The Suffolk SPCA announced last week it has begun offering training for members of the public willing to serve as volunteer animal welfare investigators. The unusual move is partly in response to the apparent ritualistic killings.