The Rules wrote:2.5 Player Versus Player
If two individuals are fighting and you have no proof which could be the traitor, you must wait before joining in the fight until one player dies and they either; identify the body/the round ends/you question them.
Kyber wrote: I followed Vojta from the start of the round and knew for a fact that he had not been KOSed, or committed any traitorous acts.
If what Kyber is saying is true, then this was not RDM. The only issue is it's impossible to tell if he's telling the truth as there's no evidence.
He did nothing wrong by joining the gunfight. If you read the rule that has already been shown and explained to you it clearly states that it only applies if you do not know which player is the traitor. In this case Kyber had proof that one of the players involved had committed no traitorous actions so no innocent player would have a reason to attack him, making his attacker an rdmer or a traitor. Joining a gunfight is not always RDM.