LONDON (AP) — An Irish nationalist lawmaker resigned from Britain's Parliament on Monday after sparking outrage by appearing to mock a massacre carried out during Northern Ireland's decades of violence.

Sinn Fein legislator Barry McElduff was shown in a Twitter video with a loaf of Kingsmill brand bread on his head, on the anniversary of the 1976 murder of 10 Protestant workmen by IRA militants in the village of Kingsmill.

McElduff said the video wasn't a reference to the slayings. But he was suspended by Sinn Fein, and announced Monday he had quit his seat in Parliament. He apologized for the "deep and unnecessary hurt" his video had caused.

The episode strained Catholic-Protestant relations in Northern Ireland at a delicate time. The power-sharing Belfast administration has been suspended for a year amid a feud between the parties.

McElduff's resignation triggers an election for the Northern Ireland seat of West Tyrone in the House of Commons. Sinn Fein members elected to Britain's Parliament refuse to take up their seats, as they don't recognize its jurisdiction over Northern Ireland.