Kevin Hrcka was pronounced dead following the noontime accident at Miron Building Supply in the Ridgewood section of Queens, police and the owners said.
The boy was waiting for his father to get off work at 1 p.m. when he found the keys in the ignition of the forklift, started the engine and drove about 100 feet before the machine flipped over and landed on Kevin, the business owners said.
Workers "rushed over with another forklift and lifted" the machine crushing Kevin off of him, said Derek Messing, the vice president of the company.
"That was it, and it was too late," he said.
Messing said he believed the boy's father might have been in a locker room changing out of his work clothes when Kevin got on the forklift.
Police said they were investigating why Kevin was on the machine, as well as what caused the forklift to tip over.
"He drove down the yard full speed and tried to make too sharp of a turn," Messing said.
Messing's father, Benny Messing, has owned the business for about 30 years. The Messings said the keys to the forklift are often kept inside the machine throughout the day so workers can use it a few minutes at a time.
"We're going to make sure there are no more unauthorized people here," Benny Messing said Saturday on Newsday's Web site.
Kevin's home phone number in Queens was unlisted.
