She thought she could take him on with the level of preparation she had made.
The sight made him think to himself, "What commendable confidence."
He knew to expect something like this because that is what she usually does, but he was still surprised that she decided to go through with it after what happened to their armored truck.
Her actions made him suspicious about what she was really up to. It is because can't believe that she intends to take him on with what she currently has.
He let that distract him while he waited for her to move far away from the bus before making his move. Then he shot her legs out from underneath her.
His bullet struck her thigh and crippled her immediately. An armor piercing round shot from a sniper can do that to someone even if they have steel skin.
