NEW YORK — A teenage subway surfer died and another was seriously injured when they fell from an L train near the Bushwick-Aberdeen station in Brooklyn on Thursday afternoon, police said.

The two 14-year-old boys were found unconscious on the rail bed when police arrived just before 2 p.m., cops said.

Both teens were found under the Manhattan-bound train, NYPD transit chief Michael Kemper told reporters.

“Both of them had serious trauma to their bodies, and tragically one was pronounced deceased on scene,” Kemper said.

The other teen was taken to Cohen Children’s Medical Center in Queens, and was “in very serious condition with serious trauma to his body,” Kemper said.

The boys are believed to have entered the subway at Broadway Junction in East New York and climbed to the roof of the L train, which at that station runs above ground.

The boys were most likely struck as the train headed underground, Kemper said — barely making it one stop away to Bushwick-Aberdeen, which is in Bushwick.

“It was as the train was entering the tunnel that we believe they made contact knocking them off the top of the train,” he said.

“This incident is tragic on so many levels,” Kemper added. “We urge anyone even thinking of subway surfing — don’t do it.”

Authorities have struggled to discourage youths from subway surfing, a sometimes deadly practice fueled by social media.

“Subway surfing kills. It kills,” Mayor Eric Adams said during a visit to the Bushwick station Thursday.

“You go online right now, put ‘New York City subway surfing’ — you will see some of our young people are watching,” he said.

“Every family member that lost a loved one to train surfing is reliving the horror today with another child who’s lost. We can do better and social media must play a role in addressing this issue,” Adams added.

Zackery Nazario, 15, was killed in February while subway surfing atop a train rumbling over the Williamsburg Bridge as his girlfriend watched in horror.

Another 15-year-old, Ka’Von Wooden, was killed in December. He was subway surfing on top of a train as it approached the Delancey St./Essex St. station on the Lower East Side when he fell under and hit the third rail.

MTA data show the deadly trend is on the rise.

In February, 52 people were caught riding outside of a subway car, according to MTA spokesman Michael Cortez. In January, 58 people were found riding outside the train. Cortez could not immediately provide more recent data.

A record-setting 928 people were caught riding outside subway cars in 2022 — more than four times as many incidents as in the previous two years.

By comparison, in 2019, the last full year of data before the pandemic tanked subway ridership, 490 people were caught riding outside a train car.