James Jones, Jr., 21, a junior studying chemistry, had responded to an ad in Craigslist to buy the phone on Monday night in Marietta, Georgia, about 20 miles north from his school.
"It was an illegitimate ad he was responding to and he did not know the sellers," Marietta Police officer David Baldwin told ABC News, adding that the posting appeared to be real. "The ad was posted in the hopes to lure somebody in, but obviously the victim didn't know that."
A court clerk told ABC News she was not aware if the defendants have hired attorneys.
Jones’ brother called him a “bright young man” who wanted to be a doctor.
“My mother lost her son. My sister lost her brother. I lost my brother. So I don’t think we can put that into words. There was a lot of heartache,” Jones’ brother Samuel Heath said.
Jones was shot and killed while he was sitting in his car, Baldwin said.
"After he was shot, the car went forward, hit another car and a tree," Baldwin said.
Police were originally dispatched to the area with a report of a motor vehicle accident.
"Through the course of the investigation, they discovered that he was going to that area in response to a Craigslist ad," Baldwin said.
"This is a devastating loss for the Clark Atlanta University family," a statement from the university read. "Mr. Jones was a serious scholar and a kind, engaging spirit whose work and comportment spoke well of the university's core values and those instilled long ago by those contributing to his upbringing. In addition to his studies, he was a UPS scholar at Fickett Elementary School and a science mentor for the HBCU Rising Cares Mentoring program at Brown Middle School. He also was an amateur athlete."
Baldwin said police "didn’t stop until all three were arrested."
"It was a heck of an undertaking and investigation but it helps to bring closure to the family. We hope to give them peace to know that everyone involved in this senseless murder will be held accountable," Baldwin said.
Craigslist did not immediately respond to ABC News’ request for comment.
A private memorial service will be held on Thursday at noon for the university community and family.