Alright, i'm going to add some pointers:

1. We want to see a LOT of combat log, to show that it's not random damage that killed you.
2. We want to see a TIME, to show that the deaths are in succession and not just a random collection of screenshots on different dates. There are addons for this
3. We want to see your CORPSE, showing that they actually KILLED you, with the bit included in your combatlog that showed who did so, at what time.
4. We want to see less threatening in lfg chat, as a corpsecamper shouldn't be warned. they should be jailed/kicked/banned. When you're being corpsecamped just go about your normal business, take proper screenshots, and don't tell them. Make a ticket telling gm's about your forum post and hope that there are any on when the corpsecamper is too, so he can be properly punished.

As for the screenshots it is hard to tell if the person was actually attacking you or if you happened to be too close to an AOE or something. Try getting a screenshot of them actually attacking you (showing their character and the skull that shows that they are way higher level than you)

If someone was to get on and investigate this there is no way to prove that at the time they were not within the proper level range at the time of the incident.

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Edit:

Careful with the accusations. It was just a misunderstanding and does not mean he is protecting his friends.