When Niko meets up with Gery, evidently, Gerry's boss wants to cause some tension between the Ancelottis and their Albanian muscle. The first step calls for Niko to assassinate some high ranking members. He wants him to kill high-ranking Ancelotti member Tony Black, AKA Anthony Spoleto.
First, go to an alley way nearby to find a car bomb that Gerald has left for you. The Ancelottis will be meeting with the Albanians in Little Italy. Tony Black's Cognoscenti is parked off an alleyway in Feldspar Street, next to Drusilla's. Get there, plant the bomb on the back of the car, and quickly find a decent car. Tony Black and another member will exit the restaurant and drive off. Follow them back to North Holland. Don't shoot them or get too close. After they arrive, they go to a old factory. Get to a safe distance and detonate the bomb. The car explodes under the gas canisters and Tony is killed in the explosion. Some gang members will survive; kill them all and get away before the LCPD arrive. The cops will almost certainly get there before you can scram, so get ready for a chase. When you lose the cops, mission passed.