So Cross was attacking Desmond when he was in Abstergo Industries and he was about to shoot Desmond when he suddenly freaked out and held his head in pain! What exactly happened to him?
Daniel Cross was suffering from the Bleeding Effect when he confronted Desmond Miles. This was why he was holding his head and speaking in Russian. Bleeding effect is a disorder wherein the genetic memories of one's ancestor begins to blend in with the person's own memories.