One, hunting bounties that are not on this board is illegal. If you were engaged in a battle with RP engagement, and managed to kill him - it would be acceptable.
Two, A screenshot off the targets ID and a screenshot of the blue kill message is required by most people, in order to confirm the kill.
Three, Nice job killing him! But I ain't claiming for him. If you have the proper ID and Ship, for example Mercenary, there are plenty of bounty boards you can appeal to; if you have the guncam images.
You can attempt to apply for these networks, as both pay for the death of Bounty Hunters. You need to be friendly to both, and agree to their rules in order to apply. I wish you luck.