What most likely happened. Is you were doing exactly what you said you were doing. You attacked 5-6 mobs that were already engaged by the other player. And I'm going to give you the benefit of the doubt and assume you did not realize the camp rules for an outdoor zone and thought you were in the right.
Here is what the other player experienced. He was trying to exp with the safety of a zone line nearby. He saw you at idol camp, and knew the rules enough to know he could take the other orcs. You repeatedly tried to steal his kills. You have an <Aftermath> guild tag. They have reputation for being NOT newbies. Therefore he assumed you knew the rules and were acting maliciously. He petitions you. GM looks at logs. Sees repeated infractions on your part. Issues 1 week suspension (usually the norm in situations like this).
When looked at like this. It does not matter what you thought, or what your intentions were. You repeatedly broke the rules, and probably showed no remorse. Did you ever send the guy a tell asking him why he was stealing your mobs? Clearly you thought he was doing so or you wouldn't have cared enough to try to kill them.