Literal translation
to make a mincing, a slaughter
Meaning
to cause a massacre
Explanation
Chapla means to cut into pieces, especially meat, and a chaplaire is a butcher's cleaver. Faire un chaple literally means committing a massacre. Figuratively it applies to someone who went overboard, like a gardener gone wild in the vegetable patch. It is also used with deliberate exaggeration, to add colour to an otherwise ordinary story. Announcing it is usually just a figure of speech : nothing actually gets broken, someone is simply about to lose their temper.