A series of threatening letters have been delivered to two LGBT community centers on Long Island.

David Kilmnick, the founder of Long Island Gay and Lesbian Youth, says four letters have been sent to the community centers in Woodbury and Bay Shore. The first arrived in June 2013, right before a pride parade was held in Huntington.

Kilmnick says the first letter threatened to attack the pride parade and referenced the 2013 Boston Marathon bombings. Other letters indicated knowing where Kilmnick lives and threatening to kill him. Kilmnick says the latest two letters threatened to burn down the LGBT senior-housing complex after it is built in Bay Shore.

Police have stepped up patrols at Kilmnick's house and the two community centers. Anyone with information on the letters is asked to call Suffolk Crime Stoppers at 1-800-220-TIPS.