Since he died from a gunshot to the mouth, I don't think he had any control over where his gun ended up.I read that the resulting explosion in the tesla would be contained like an implosion and "up". I am sure ML knew this, so he put those important things like his guns and documents down on the ground at his feet.
ETA Actually, didn't he have 2 guns with him? So one of them, he may have placed on the floor, but the other one must have ended up wherever it fell after he shot himself.