As has already been mentioned, they had no timeouts left.
Someone questioned why Rondo was in the game with 7 seconds left.
Answer: because he is the team's point guard!
Now, if he had attempted a rapid drive to the hole, one of the defenders may have bit and collapsed on him thereby leaving someone open on the wing for a kick out and better last three-point attempt than we got. It was a poorly executed last play under heavy pressure.