Go to the Majestic Hotel in Lower Middle Park. In the lobby, you will find a set of elevators. Call them and you will be brought to the 30th floor. Isaac and the other two targets are on different levels of the penthouse. Fight your way through Isaac's muscle. The first target will be in the kitchen. Go up a flight of stairs to find the second target in his bedroom (he'll be sending his girl out; you can kill her or let her go). Isaac and some more of his will be on the roof. Finish them off and escape the hotel as you will have a two star wanted level.