[He's always prepared for the long haul, which is lucky for Joshua. He's also well aware that this 'Callaghan' person has his own story, but he's not heartless enough to say anything of the sort to Hiro in this moment.]

Thus, you blame Callaghan for not doing a single thing to prevent your brother's death and for making his sacrifice completely in vain. You blame yourself for as many reasons as there are colors in the world. And you blame Tadashi for being a hero because it cost him his life. Possibly, you even blame others for not stopping him or not arriving fast enough.