A: I’ve never seen Mary have an outburst before. She scared me this morning.

B: She can be as jolly and matey as you please off duty but if she ought to come down on anyone she comes down like a ton of bricks.

Note: This idiom means “with great force, severely,” used especially of the manner of punishing or reprimanding someone. It’s a vivid metaphor easy to understand since a ton of bricks is literally something hard and heavy. For example: When he spotted my mistake he came down on me like a ton of bricks.