Who attacks Mark as he goes to join Alec in the cockpit in Chapter 44? How does Alec save Mark?

Mark joins Alec in the cockpit. But a man has climbed up on the Berg, and has used a hammer to shatter some of the glass. Mark goes to handle him, but is almost pulled out. Alec uses the hammer to knock the attacker from the Berg, and then with Mark safely inside the Berg, takes off to the sky.