The reputed head of New York's Gambino crime family, Frank Cali, has been killed outside his home, the city's police have told US media.
Cali, 53, was shot several times in the Todt Hill district of Staten Island on Wednesday evening and died later in hospital.
The unidentified killer fled the scene in a blue car, witnesses said.
New York media say it is the first targeted killing of a mob boss in the city since 1985.
The Gambino operation is said to be one of the five historic Italian-US mafia families in New York.
Witnesses said Cali's killer shot him at least six times and then ran him over before fleeing the scene. Family members were seen to rush into the street and sit crying next to his body.
Police said the motive was not known.
"There are no arrests and the investigation is ongoing," a statement said.
New York media say it is the first killing of a family boss in the city since the Gambino family's Paul Castellano was shot dead outside a restaurant in 1985.
Francesco "Franky Boy" Cali is said to have taken over the running of the organisation from Domenico Cefalu in 2015.
It is believed he only had one criminal conviction, for conspiring to extort money in 2008 for which he served 16 months in prison.
Perhaps the most notorious head of the Gambino family was John Gotti, who was convicted in 1992 of 13 murders and a litany of other offences. He died in 2002.
Staten Island's affluent Todt Hill neighbourhood is renowned for its crime connections. It was used as the location for fictional crime boss Don Corleone's compound in the 1972 film The Godfather. Paul Castellano also owned a home there.
The Genovese, Gambino, Lucchese, Colombo and Bonanno mafia families are believed to have controlled organised crime in New York for decades.
Last week, Carmine Persico, the 85-year-old former boss of the Colombo organisation, died after serving 33 years of a 139-year prison sentence.
On Wednesday, two heads of the Bonanno family, Joseph Cammarano Jr and John Zancocchio, were acquitted in a Manhattan court of racketeering and conspiracy to commit extortion.