Mission 32 – Rob the Warehouse
There's a locked blue door on the east side of building. The guy in the chair seems strangely reluctantly to leave it, no matter how you whistle, so a bullet in the back of the head both takes him off the board, and attracts everyone else to your chosen kill zone.
When everyone is dead, take the money from the poker table and skedaddle- there's nothing else going on here.