UPDATE: Arrest made.
Transit Police have released photos of a guy they say arranged over social media to meet somebody with an "expensive iPhone" to sell - which they say he then stole at knifepoint.
The robbery happened around 6:20 p.m. on May 12 at the Shawmut stop on the Red Line.
The suspect in this matter responded to the victim's ad and requested the victim conduct the exchange at an MBTA station. The victim agreed and was subsequently robbed and assaulted. Unfortunately this scenario has played out several times in the past.
Transit Police say anybody arranging a purchase or sale of an expensive item online can use the lobby of their Southampton Street headquarters. Boston Police recently announced "safe exchange zone" areas for this purpose at its headquarters and district stations.
If the Shawmut guy looks familiar, you can contact detectives at 617-222-1050 or send an anonymous text tip to 873873.