In the Harry Potter Book The Order of Phoenix what did Mundungus Fletcher do to make Mrs Figg say she was going kill him?

In Harry Potter and the Order of the Phoenix, Mundungus Fletcher stole Mrs. Figg's prized possession: her cat, Mr. Tibbles.

This angered Mrs. Figg greatly, to the point where she threatened to "kill" him, though she was known for her rather colorful language.