First of all, LETS NO KID OURSELVES about the license plate. It is very possible it was swapped. Is there any other information that you can give us to identify the car or is it otherwise unremarkable? Perhaps any leads on what the people look like?
Fortunately these are fairly rare in CA and it may be spotted!
Lastly... I am very sorry for your loss and recognize nothing you will hear will make you feel any better other than maybe "WE GOT EM". So so sorry.