(Photo: Facebook/Scott Christian Leisner)Michael Leisner of Minneapolis, Minn., who protested General Mills' support of same-sex marriage by setting a Cheerios box on fire in front of the General Mills Headquarters, died Saturday, August 11 of a heart attack. He was 65 years old.

Michael Leisner, the "cereal arsonist" who set fire to a box of Cheerios cereal in front of the Minn. General Mills' headquarters last week in protest of same-sex marriage, has died of a heart attack. He was 65 years old.

Leisner's pastor Dwight Denyes of the Emmaneul Christian Center told media outlets that the 65-year-old real estate broker passed away Saturday, Aug. 11 while waiting in his car for his children to finish playing tennis near his Andover, Minn. home.

Pastor Denyes told the Minneapolis Star Tribune that Leisner "was a very loving and caring father of his four children, a loving husband and he seemed to get along with other people."

In a statement released to the Minneapolis Star Tribune, the family says that Leisner's two children came back to the car and found their father not breathing. He died shortly after at Mercy Hospital in Coon Rapids, having suffered a "massive heart attack."

"Yesterday, a man called Mike Leisner, who was my spiritual father, died. He had the courage of a Lion for God, [and] some remembered him as a fiery Elijah with the boldness of John the Baptist," Scott Christian Leisner, who is Michael Leisner's nephew and works as a Christian missionary in Costa Rica, wrote in a tribute Facebook post.

Leisner gained internet fame from an Aug. 5 YouTube video, filmed by one of his sons, which featured the 65-year-old Christian torching a box of Honeynut Cheerios in front of the General Mills headquarters in Golden Valley, Minn.

"One out of every eight boxes of cereal in this country is Cheerios. This is really the treat, now, for the homosexuals," Leisner tells the camera.

"And this is our protest against General Mills [for] advocating same-sex marriages. So we are gonna torch some cereal," he adds.

Although Leisner intended to torch only the cereal itself, he accidentally torched the entire box. He then is seen frantically trying to stamp out the flames as they spread to the bowl and the grass in front of the General Mills building.

Noticing that the fire had become unruly, Leisner then tells his sons to get in the car and they flee from the scene.

General Mills has been an outspoken proponent of same-sex marriage, with CEO Ken Powell donating money to pro-same sex marriage organizations and speaking out against Minnesota's proposed November 2012 amendment that would ban gay marriage.

Leisner initially faced possible criminal charges for setting fire to the front lawn of General Mills, but after his death, the investigation has been "exceptionally closed," police told The Smoking Gun.

Leisner's funeral service is scheduled for Friday, Aug. 17 at the Emmanuel Christian Center in Spring Lake Park, near Minneapolis, Minn.