A 39-year-old man was killed when he crashed his snowmobile on Lake Hopatcong in Jefferson, authorities said.

Brian Petronaci of Hopatcong was operating his snowmobile when it struck a rock near Liffy Island in Jefferson and crashed into trees, according to a preliminary investigation by Jefferson police.

Petronaci was pronounced dead at 2:30 a.m. Sunday at the scene of the crash, Jefferson Police Detective Joe Kratzel said.

Kratzel did not know when the crash occurred, but said officers were asked to assist Hopatcong police at 1:40 a.m. in searching for a missing person operating a snowmobile on the lake.

Liffy Island is located across from the Lake Forrest Yacht Club in Jefferson.

Rob Jennings may be reached at rjennings@njadvancemedia.com. Follow him on Twitter @RobJenningsNJ. Find NJ.com on Facebook