Because there are so many people who either don't know what the RDM rules are or don't understand English, I'm going to offer a copy-pasta you can refer to when you're confused about whether someone has to jump out in front of their enemy, flourish their cape, and shout about their name and how they're here to avenge their father.
RDM - Attacking another player/group without any story/roleplay leading up to it.
The key phrase here, the phrase that determines whether an attack is random or not, is "WITHOUT ANY STORY/ROLEPLAY LEADING UP TO IT."
That phrase does not mean there has to be roleplaying (dialogue/in-character statement) immediately preceding an attack from one character on another; it means there must be an in-character basis for the attack on the part of the attacker.