Leary was booked Wednesday night on charges of statutory rape and endangering the welfare of a child. Under New Jersey law, the 15-year-old is too young to consent to sex.
Leary was being held Thursday in jail on a $200,000 cash bond.
Police said they are investigating whether Leary was involved with the rape of the 7-year-old at a party Sunday night in a public housing apartment building.
On Thursday morning, police on unrelated outstanding warrants during a sweep of Rowan Towers. Capt. Joseph Juniak said the raid was planned before the girl's attack but that it was "somewhat beneficial for investigators" looking into the child rape.
Police believe as many as a dozen people were at the party and said that everyone in the apartment when the rape occurred could be legally culpable.
At the party, the 15-year-old starting having sex with several men for money and then gave the younger girl some cash to let a group of men touch her, police said. It soon escalated to rape and the men threatened to kill the child if she screamed or told anyone, according to police.
Police are reviewing surveillance videos at the complex.
According to police, the teenager and the 7-year-old were outside in the neighborhood Sunday when the older girl ran into two young men she knew who invited her to the party. The 7-year-old wanted to tag along because she was worried about the older girl's safety.
The 7-year-old later put on her clothes and left the apartment; her older sister stayed. Two women found the child crying outside the apartment and walked her home.
The teenager's name was not released because of her age, but the county prosecutor plans to ask the court to try her as an adult. It was not clear who was representing the girl in juvenile court.
MORE ON CRIMESIDER