Michael Leisner, whose August 5th protest of General Mills resulted in a viral video, died Saturday after suffering a heart attack.

Leisner's protest, which involved igniting a box of Cheerios outside General Mills Golden Valley headquarters, against the company's opposition of the marriage amendment, the Star Tribune Reported.

According to his pastor, Dwight Denyes, Leisner died in his car while waiting to pick up his sons from tennis practice. A statement released by Leisner's family said his sons found him in the car, not breathing, and was then taken to Mercy Hospital in Coon Rapids.

A video taken of the protest by Leisner's friends was posted online and "caused a sensation among the LGBT blogosphere," the Huffington Post reported. According to the Star Tribune, the video was shown on the Daily Show and Chelsea Lately.

The Huffington Post reported that the video also prompted a police investigation, which ended following Leisner's death.