Why Did Gregory Kill Cassie in FNAF: Security Breach — Ruin?

In one of the endings for 'FNAF: Security Breach — Ruin,' players watch as Gregory betrays and supposedly kills Cassie during her escape. But why did he do it?

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Who is Cassie in FNAF Ruin and what will happen in Ruin solved

Gregory is REALLY crying for help..

Why Did Gregory Betray Cassie In FNAF Security Ruin?

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Gregory Gets Destroyed By Cassie Five Nights At Freddy's Security

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Why Did Glamrock Freddy Turn Evil In FNAF Ruin?

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Why Did Gregory Kill Cassie in FNAF: Security Breach — Ruin?

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