he got injured and Melissa will later find him and bring him back, he actually turns out to be a werewolf and possibly from the same family as Jack because if you noticed their last names are the same though I'm not sure yet, and if it's true it would make sense why they're fighting.
when she found him it was actually accidentally I think, also, he will be injured in his wolf form, I think he got in his wolf form so he won't get as much damage as he would in his human form.
one last thing, I know I was saying "werewolf" this whole time but I'm not exactly sure yet, he might be and he might not be, though he probably is a werewolf since he will turn into his wolf form and he has the same last name as Jack (that red werewolf).
oh and when I said "family" they don't have to be like brothers or something, they could be relatives.
and if in Melissa's novel world exist "clans" for the werewolves then it would make even more sense. so Nine and Jack might not be related by blood but they're from the same clan.