Baton Rouge police say they've arrested 17-year-old Ray Juan Martin on four-counts of armed robbery.
Two of the robberies involved victims who advertised goods on Craigslist.
In one instance, the victim was selling iPhones and iPads, while a second victim was selling an iPhone.
Sergeant Don Kelly says police allege that Martin was one of two or three suspects who robbed the victims of cash and property, and in one instance, the victim's car.
Kelly says additional arrests are expected.