Usually, no. Throwing a gun doesn't usually happen. I'm surprised you brought that one up given that so many folks think everyone in the USA has a gun anyway. Why would I throw a gun to someone who probably has one already?
But in fact, guns aren't THAT common over here despite the lurid headlines. Now dropping a gun that happens to have a sensitive trigger? That will happen now and then, and if the bullet kills someone as a result, the person who dropped it might be charged with negligent homicide.