As we know the old guy looking out on downtown Los Santos used to have a criminal lifestyle, and he moved to Los Santos with his kids to escape his past basicly.
But have you noticed he doesn't mention his wife or girlfreind. I think that she died.
Now enough of fact, and time for theory.
I think the young man we see in the trailer, driving the blue sports car, and robbing the jewellery store is actually the old mans son. I think this because they both look the same, with there hair line etc.
But why would he be robbing?
I think he is stressed out with his mums death, and the only person he has to look up too is his "criminal" dad. And he goes out and robs, for his dad, who pursuades him to rob.
Dont hate, if you dont agree, atleast I am contributing.