JD had a tip-off that LCPD is going to do a raid on the club, and the problem is worse - Salvatore is paying a "special" visit. You need to get Salvatore back safely to his mansion.
Saving the Don
After getting into the Leone Sentinel transporting him, you need to lose that wanted level. Your best bet is to take the long way round to the near Pay N Spray before dropping Sal off. He tells you that he has some work when you need it.
You are able to purchase the Micro SMG for $600 at AmmuNation.