Cali was gunned down outside his home in Staten Island, New York, Wednesday, cops said.
Police have a 24-year-old suspect in custody in the slaying of reputed Mafia boss Francesco "Franky Boy" Cali in New York City. "We are at the beginning stages of this investigation", Shea said.
Cali, 53, was a high-ranking member of the Gambino organized crime family and was believed to be the acting boss, a law enforcement source confirmed.
Comello's fingerprints were found on Cali's license plate, sources said.
The suspect "is now being held in jail in New Jersey pending court appearances, where we anticipate we will have him returned to Staten Island to face murder charges for the death of Francesco Cali, which occurred on this past Wednesday evening", Shea said.
Surveillance video of the killing showed a man, allegedly Mr Comello, crash his vehicle into Mr Cali's parked SUV, drawing Mr Cali outside in what might have been a ploy to lure him out of the house, Mr Shea said.
Police said surveillance video captures the shooter, and the pick-up believed to be the getaway truck. An assistant DA there referred a reporter to the office's public information officer, who was not immediately available.
Cali shunned the limelight even after becoming don, ruling from the top while lying low in his affluent Staten Island district, where Castellano also held court.
Shea said the motive for the killing is unknown.
Cali's only mob-related criminal conviction came a decade ago, when he pleaded guilty in an extortion scheme involving a failed attempt to build a NASCAR track on Staten Island.
Angel Gotti was referring to early speculation that her uncle Gene Gotti, just released from prison past year, was somehow behind the hit, in some kind of power struggle. He was sentenced to 16 months behind bars and was released in 2009.