NEW YORK (CNN) -- It was supposed to be an ordinary buy-and-sell: a Brooklyn teenager buying sneakers from a seller he encountered on craigslist.
But the Friday afternoon transaction turned out wildly different -- an alleged armed robbery culminating with the teenage suspect's arm severed after an SUV ran over him, according to New York police.
Police say Zachary Sam, 17, met up with Philipp Pierre, 39, to buy a pair of $200 Air Jordan Retro 8 sneakers.
But once inside Pierre's gray Honda Pilot SUV, Sam allegedly pulled a black revolver, pointed it at the man and demanded the sneakers as well as cash, according to Detective Annette Shelton, a police spokeswoman.
Video surveillance obtained by CNN affiliate WABC shows the teen walking across with the street with what police say was the loot as the SUV drives away.
Sam is then seen walking on the other side of the street when the SUV speeds up from behind and runs him over, the video shows.
The teen's arm was severed as the SUV pushed him forward and ran over him, police said.
The video shows the teen picking himself up despite his injury, running toward an MTA bus down the street and trying to board it, Shelton told CNN.
Sam was pulled off of the bus and continued to flee until he collapsed, Shelton said.
He was brought to Brookdale Hospital, along with his arm, and is listed in serious but stable condition, Shelton said.
Sam was charged as an adult with criminal possession of a firearm and second-degree robbery, according to the NYPD.
Pierre was charged with second-degree attempted murder.
An identified man who said he's a cousin of Pierre told CNN affiliate WPIX that he sells the sneakers as a way to "support his family."
Attempts to reach Sam, Pierre and their families were not successful.
A man, identified only as Michael, who said he is related to Sam told WABC: "Two families are destroyed tonight -- my cousin, and this kid's family."