Other source:

Goku explains to Master Roshi, Tienshinhan, Krillin, and Yamcha that Hero was actually Kami in a human body. He tells them about Kami and Piccolo splitting into two separate entities, good and evil. Goku realizes that it is up to him to stop Piccolo now. As their match begins, their strength appears to be equal. Soon, however, Piccolo unleashes a flurry of attacks that leaves Goku lying in a hole as the count rises.