POTOMAC, Md. (AP) — Montgomery County police say a man hiking on an island in the Potomac River was killed when a boulder fell on him.

It happened about 4:40 p.m. Sunday on Offutt Island, which is downstream from Great Falls. Officers say 25-year-old Rian Khalder of Silver Spring was hiking with his 14-year-old brother.

Police say Khalder was climbing rocks when they gave way. Authorities say a large boulder fell on Khalder, killing him.

Authorities say the Office of the Chief Medical Examiner in Baltimore will determine the cause of death.

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