Michael McCain, the chief executive of a Canadian meat processor, Maple Leaf Foods, strongly criticized President Trump and his foreign policy on Twitter on Sunday night.

In tweets published on the company’s official account but signed by him, Mr. McCain blamed “U.S. government leaders” and “a narcissist in Washington” for policies that led to last week’s downing of a jetliner near Tehran, killing all 176 people on board, including 57 Canadians.

Among the dead, Mr. McCain said, was the family of a Maple Leaf Foods colleague.

The plane was shot down as tensions escalated after the United States killed an Iranian military commander, Maj. Gen. Qassim Suleimani. Iranian leaders eventually conceded that they had shot the aircraft down and said it was a human error.