Ink tin foil hat theory...
What if Ink stumbled across something and then knew that the outbreak was going to start? Something along the lines of "Hm...there is no cover page on this random TPS report left on the printer. I'm gonna read it" and that leads him to another thing and then another and he realizes that the outbreak is going to happen no matter what. STICK WITH ME! If your spouse were to then cheat on you and you knew the end of the world was around the corner...what would you do?? What I think Ink did is decide to do was get revenge 10 fold since it wouldn't matter once the outbreak started. So he then gets arrested, and what is the best way for people to think you are bat shit crazy? Tell them it's the end of the world! Now he is sitting in the jail and thinks to himself....I've always wanted a tattoo! He gets himself an impressive array of randomness all over his face, hands, etc. Next thing he knows, he is sitting in the back of the van and sees zombies are coming for him. What does he do? He puts on some powerman 5000 and lets it happen.!

Ok, Maybe some holes in this! I have no clue about the tattoos or why he ended up different. But the murders and plea I think make some sense.