Lets look at the rule:
RDM is killing/downing another player without any type of HOSTILE role-play being initiated and reasonable amount of time for the target to react.
If you rook a dude in the leg and he doesnt die, you are not killing/downing him. However doing so is a huge risk, as the dude you are shooting might have 1HP before you shoot him and you then kill him, which is RDM.