Authorities say Charles Santiago was arrested on Saturday. Another man, Joseph Gencarelli, was arrested last week and is being held without bail.
Police believe robbery was the motive. They are still looking for more suspects in the case.
Antonelli was a married father of two. He was shot in the chest and stomach.
The shooters, described as two white men in gray sweatsuits, did not take any of the jewelry the victim was carrying, leading investigators believe Antonelli was targeted.
Antonelli had recently celebrated the birth of his daughter.
"Why would somebody do this," son Louis Antonelli, Jr. asked the day after the shooting. "My dad was friends with everybody. Why would they do this?"
Wife Jennifer Antonelli said the shooting makes absolutely no sense. She said her husband was well-known and well-liked. She said he even rescued a neighbor from a house fire in 2000.
"When you're well known, and a lot of people know you and they know your business, and they know about you, you're going to have people who are jealous and enviousof you," she said.
Antonelli was also an honorary member of the Sea Gate Police Department, which is not related to the NYPD. Sea Gate is a private, gated community on the far west end of Coney Island.
Antonelli apparently worked as a volunteer for the PBA. Authorities say he was given the honorary member title from the deputy chief for all the work he has done in the department.
