If you have a lethal pistol on you and you are carrying a sting or any other taser, there is a glitch where your taser will turn into a lethal until you drop that pistol on the floor or in a vehicle. Not sure if it happens 100% of the time though.
You cannot log off if you get rdmed. You just need to submit a player report and compensation request with the proper evidence and everything will be fine. Just because someone else breaks a rule it doesnt allow you to break rules also. You can still get banned for combat logging if you got rdm tased. Just record and report, its that simple.