A man was carjacked at Harbor Point late Wednesday afternoon by somebody who had contacted him over SnapChat, allegedly to buy sneakers from him, according to an alert sent out by UMass Boston police.

According to the bulletin, the victim pulled up in his car and the alleged buyer got in and then "assaulted him with a handgun, stole the vehicle and fled toward Westwind Road and Island View Place."

Boston Police Department officers responded to the scene 66 Peninsula Pl. shortly after 5 p.m. The stolen vehicle was reported as a gray 2014 Honda Pilot. The attacker was described as mixed race, with short dreadlocks and wearing a purple jacket with a hoodie. His gun was black with an extended barrel.

This is the second time in a week somebody trying to sell something was robbed in Boston. On March 29, police report a person was robbed at 330 Rutherford Ave. in Charlestown by a man who had agreed to meet there to consummate a purchase arranged on Facebook Marketplace.

Police have set up "safe exchange zones" at BPD headquarters in Roxbury and at every district station where people can buy and sell stuff 24 hours a day while knowing the areas are monitored by police.