No problem killing PCs but that is not a rule.
If a player, even facing almost certain death, comes up with a great idea and acts in a tremendous way I would not have him killed unless there are no other way.
In regular situation, death is always close.
If a player get painful (in some way; choose which one
), He'll be quickly killed and he 'll find out that someone can be killed by a stone dropping from the sky in the middle of a flat desert. Actually, he'll have a good chance to face a platoon of T-90 supported by heavy artillery while having only a single empty pistol.
To give you an idea, I end up with dead character even when I GM starwars.
