Disturbing video shows gruesome subway surfing incident that killed 1 in NYC — as the other gravely injured

Brutal video obtained by The Post reveals how a gruesome, fatal subway surfing incident in Lower Manhattan unfolded.

The clip shows the 14-year-old boy and his 18-year-old pal on the top of the J train as it zoomed along in Lower Manhattan Friday – before one of them is struck in the head by a beam.

The clip shows the 14-year-old boy and his 18-year-old pal on the top of the J train as it zoomed along in Lower Manhattan Friday – before one of them is struck in the head by a beam.

The footage shows both falling to the rails and ground below.

The 14-year-old boy was killed and the 18-year-old was gravely injured, cops said.

The younger teen died as a result of injuries consistent with a fall.

The older surfer was rushed to Bellevue Hospital in critical condition.