A Newark man is under arrest for allegedly putting 78-year-old former Newark Mayor Sharpe James in a choke hold and stealing his gold chain.

The suspect apparently had a hand in getting himself arrested.

Newark police arrested 20-year-old Alhafeez Williams after he approached Port Authority Police officers at a New York City subway station and asked them if he could have a free ride back to Newark to meet with his parole officer. Port Authority police officers recognized him as a the prime suspect in the Sharpe James mugging.

"Our officers were a little suspicious," Port Authority Police spokesman Steve Coleman told ABC News. "They checked into this guy's ID and found he was wanted in connection with the Sharpe James robbery."

Port Authority officers then accompanied Williams and his girlfriend onto the train back to Newark, where he was arrested by the Newark Police.

"We let the guy get his free ride back to Newark and when the train pulled into the Hobken station, it was met by Newark police detectives," Coleman added.

Newark police say Williams attacked former Newark Mayor Sharpe James from behind last Thursday, putting him in a choke hold and escaping on foot with the former mayor's gold chain. James was not injured in the attack.

James was elected Newark mayor in 1986 and served five four-year terms, simultaneously serving as a state senator from 1999-2008, before being convicted of fraud in 2008 by a federal grand jury. He was sentenced to 27 months in prison.

Local residents told ABC News affiliate WABC they were surprised by the attack

"Got the ex-mayor out here, minding his business and these, whoever they are, thugs, it is totally unnecessary," said one resident.

"Today's arrest was the culmination of great police work, community involvement, and technological advances," Newark police Director Samuel DeMao said in a statement. " I am pleased that through the relentless efforts of our detectives assigned to the robbery squad and the assistance of the community we were able to make a swift identification and apprehension in this case."

Williams, who has several prior arrests and felony convictions, is being held on $50,000 bail. According to the Essex County District Attorney's office, he does not currently have an attorney and will be arraigned this Monday in Superior Court.

Newark Police Department