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?

Cassie, Five Nights at Freddy's Wiki

Five Nights at Freddy's Security Breach - RUIN

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FNAF: Security Breach Ruin DLC - What Is The Mimic & Who Is Helpi?

After the Ruin (MY AU)

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FNAF SB Ruin - All Endings Explained; Scooper Ending and More

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