I'm a bit concerned about the ear-witness testimony, whereby shots/bangs and terrible screams heard. When we're discussing what a normal person would do, I would have to go and find out what was happening. Yet, the couple just went back to sleep and went to work the next day. If it was that bad, is it reasonable that you would just go back to sleep?
We need to bear in mind that it can't be entirely convincing to argue that OP shouldn't be overly concerned about security because it's a safe contained patrolled estate, and then to argue that people wouldn't have gone from their house to check it out because it's a dangerous environment.
They lived in a different secured estate and both of them called their security to notify them that they had heard screams and shots, they couldn't exactly just run over there, to which their security basically said oh well, not our concern..... As for whether they eventually were able to contact 911 type services or OP's own security about it, I can't verify off the top of my head but I'm pretty sure they tried.