Always clear the weapon even if you were the last person to touch it. That should just become an automatic motor skill. If I lay a gun down on my bench, or on the dresser, or anywhere and loose contact with it for even a few moments, I always clear it or press check it immediately when I pick it up. It's just a habit, but it's a habit that save you a whole lot of heartache. When I hand a weapon to another person, I clear it first. When they hand a weapon to me, I clear it first, even if I just watched them do the same thing. It's just a habit. It's always the weapon you think is unloaded that accidently shoots someone. Always treat ever gun as if it were loaded, and if it's a new gun to you and you are not sure how everything works, for heavens sake get someone to walk you through it a couple of times before you take it on yourself. I'd also suggest that perhaps a public parking lot isn't the best place to break it down, either!