Board Thread:Skyrim/@comment-108.31.169.175-20150421192321/@comment-6881629-20150422094152

Someone on GameFAQs had a similar problem all the replys they got were jokes though, it could be caused by a mod. You could try opening the console before he hits the guard clicking on him and using the command -

resetai

That would hopefully make him forget whatever reason he had for attacking the guard or you could skip meeting him a town with -

setstage DLC2EbonyWarriorQuest 100