A teen playing with a gun on a Manhattan rooftop shot his pal in the hand Monday morning, according to cops and police sources.

The 18-year-old and his friend, the same age, were on a rooftop on East 78th Street near Second Avenue around 8:20 a.m. when he was fiddling with a gun and accidentally shot his friend in the right hand, according to the sources.

The victim was taken to Weill Cornell Medical Center with non-life-threatening injuries.

The alleged shooter was taken into custody, with charges pending.

A gun, as well as one 9mm shell casing, were recovered on the roof of the building, police sources said.

“I heard a bang this morning, and turned to my wife and asked, ‘Was that a gunshot?’” said Glenn Garcelona, 31, a first-floor tenant of the building. “ I looked through the peephole and I saw a gentleman running. I guess it was him.”

He said he had spoken to the alleged shooter before. 

“He did tell me he would go on the roof,” Barcelona said. “I would see him on the stoop smoking weed.”

“Seems like something like that was an accident,” he added. “He seems like he was of age, just wasn’t responsible.”

Stephano Kim, owner of La Mode 1st Cleaners down the block, said he “saw someone get arrested this morning.”

“The police blocked the street and I saw at least 10 police officers running around searching the basements on the block. I was worried,” he said. “It’s not as safe here anymore. I close my door now.”

Fani Chen, 26, a college student who lives on the third floor, said she pays $2,000 for a one-bedroom apartment in the building.

“It really makes you wonder,” she said. “This is a prewar building … rents are really expensive. Maybe a doorman building has cameras to keep people safe, and maybe I will have to save money to move to a nicer apartment.”