Watching his best friend, Carter Kettner, right, grow sick and die of cancer at age 6 fuels Ben Keaty in his quest to honor Carter by finishing a cancer run.

Courtesy of Keaty family

With exotic animals all around them during this visit to the zoo, best friends Carter Kettner, right, and Ben Keaty find the invading cicadas very fascinating.

Courtesy of Keaty family

The perfectly happy childhood Carter Kettner relished in the fall of 2008 was shattered four months later when the boy was diagnosed with the brain cancer that would kill him at age 6.

Courtesy of Kettner family

The perfectly happy childhood Carter Kettner relished in the fall of 2008 was shattered four months later when the boy was diagnosed with the brain cancer that would kill him at age 6.

Courtesy of Kettner family