It started with a question on Canada's military mission in Iraq. It ended in tears.

The question came Tuesday from NDP Leader Tom Mulcair in the House of Commons question period. In response, Conservative MP Paul Calandra, filling in for Prime Minister Stephen Harper, launched an attack on the NDP's position on Israel, based on a Facebook post purportedly written by a party worker.

Faced with a repeat of the question, Calandra launched the attack again — and provided fresh fodder for the seemingly perpetual debate over the state of Canadian parliamentary democracy.

So off-topic and ad hominem was the response that Mulcair called on Commons Speaker Andrew Scheer to intervene. When that didn't work, Mulcair openly questioned the Speaker's "neutrality."

(Mobile users, watch the video here.)

Calandra appeared similarly unrepentant when he was scrummed by reporters outside the weekly Conservative caucus the next day.

(Mobile users, watch the video here.)

Appearing on CBC News Network's Power & Politics later Wednesday, Calandra defended his actions with such vigour the camera caught fellow panelist and NDP MP Paul Dewar briefly covering his face with his hands in despairing frustration.

(Mobile users, watch the video here.)

But at some point over the intervening two days, however, Calandra had a change of heart. On Friday, he rose in the House to offer a tearful apology for his conduct:

(Mobile users, watch the video here.)

Mulcair accepted the apology, but said his party will go ahead with a motion next week to give the Speaker more powers to require real answers in question period.

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