Never gotten all six. That's kind of rare for them all to be clustered together unless they might perhaps be on a fireteam. I managed to get 5 out of the 6 on Shores of Time with a golden gun. I have the explosive perk so I fired two shots into their gathering around the heavy ammo by B. I saw that Slayer and it brought a small tear to my eye. Only time that will probably ever happen to me lol