Pictures show the graffiti left behind on walls, benches, and walkways at the Shrine of Our Lady of the Island on Eastport Manor Road.
Police believe it happened sometime between last Friday and Saturday.
Suffolk County Crime Stoppers is offering a $5,000 reward for information leading to an arrest.
Anyone with information about these incidents can contact Suffolk County Crime Stoppers to submit an anonymous tip by calling 1-800-220-TIPS, texting "SCPD" and your message to "CRIMES" (274637) or by email at www.tipsubmit.com.
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