Credit goes to a YouTube video I saw called "How Tigerclaw got his ideas."
"How could you, Tigerstar. You tried to kill Bluestar, you're trying to rule the forest…What drove you to be so evil?" Firestar demanded. Tigerstar smiled.
"You know Redtail, that old deputy of Bluestar's? You can give the thanks to him. You see, the day before the Riverclan battle…"
~Before the Riverclan battle many moons ago…~
"'I figured it out, Tigerclaw! I know what's up your sleeve!' yowled Redtail triumphantly. At that time I was thinking, 'what is he talking about?' 'I know what you're trying to do!' he continued. 'You're going to kill me so you can become deputy! Then you're going to kill Bluestar! Then you'll try to take over the whole forest! And meet up with Bloodclan!' Obviously, I was just going to ask if I could borrow a chocolate bar. But I liked his idea a whole lot better. And that's what brought me to this point."
~back to reality before Lionclan battles Tigerclan~
"Oh. That makes sense." Firestar agreed. Scourge padded over to Tigerstar.
"But apparently Redtail forgot the part where I kill you." Scourge meowed.
"What?" Tigerstar mewed.
SLASH!
"You…killed him…" Firestar stared in disbelief. Scourge smiled a toothy grin. "I will rule you all now!" Just then Scourge was eaten by Tigerstar's spirit, then Scourge's spirit ate everyone.