Time seemed to stand still as Marcus' non-existent brain struggled to figure out how to deal with the six energy slashes heading his way. While they wouldn't kill him, if just one of the attacks hit him it might put him out of action long enough for the guards to deal with him.
His first thought was to dodge them, just as he had done before. But this time there were too many of them and not enough space in the corridor to move properly. He also thought of turning on his heels, running, and getting out of the corridor. But the attacks would catch up with him before he had even taken two steps.
His second option was to counter the energy slashes with a stronger attack. But the zero and 1st level spells weren't powerful enough to do that, and the 2nd and 3rd level spells required a longer activation time. By the time he had finished casting the spell, his body would have already been sliced to pieces.