A tree trimmer was seriously injured Tuesday when his harness broke and he fell about 35 feet to the ground in Deer Park, Suffolk County police said.

The man was hired to work on a tree outside a house on West 4th Street near Park Avenue, where the accident happened at 9:26 a.m., police said.

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A Suffolk County police helicopter landed in the parking lot of the nearby May Moore Elementary School and flew the man to Stony Brook University Medical Center, police said.

Police said his injuries were serious.

The Occupational Safety and Health Administration is investigating, police said.