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A 24-year-old Staten Island man who was taken into police custody on Saturday in connection with the fatal shooting of the reputed boss of the Gambino crime family faces murder charges, according to court records and officials.

The brazen shooting of the boss, Francesco Cali, in front of his home in the Todt Hill section of Staten Island on Wednesday shocked residents and longtime observers of the Mafia alike, and fueled speculation that New York City was seeing the return of open mob conflict that last erupted decades ago.

Several officials, however, said on Saturday that preliminary information suggested that the killing of Mr. Cali, 53, was not related to organized crime. One official cautioned that the inquiry was still in its early stages.

The last time a high-ranking Mafia figure like Mr. Cali was murdered was in 1985, when the Gambino chief Paul Castellano was assassinated in front of a high-end Manhattan steakhouse on the orders of John J. Gotti. The hit led to Mr. Gotti’s ascent to the head of the Gambino organization and touched off years of instability and internecine conflict.