Toni's ma thinks she knows why he's not moving back in - the Triads are giving him problems when Toni knows for a fact they are not. You have to prove yourself by killing a few.
There are 2 enemy spots at Chinatown - one target is cruising in a Bulletproof Fish Van and the rest are at the Chinatown Plaza. To neutralize the Bulletproof cruisers, ram the van until it is on fire, before finishing the targets. You then need to just make mincemeat of the rest standing around to finish up.
Your only reward sustenance is to pick up the Triads' dropped weapons and money.