Why did Kane turn on the Undertaker?

Following months of speculation, Kane made his first appearance on Oct. 5, 1997, at Bad Blood. There, he ripped the cage door off during the first-ever Hell in a Cell Match between Shawn Michaels and Undertaker. Kane and Undertaker then stood toe to toe during a chilling stare-down. The Big Red Monster wore a mask, and he hid his body in attire designed to conceal hideous burns from a fire supposedly started by his half-brother Undertaker. Then, Kane kicked the Deadman in the stomach and Tombstoned him — allowing a bloody Michaels to pin Undertaker for the victory.