WillIan Afton is the main antagonist of What happend at Freddy's. he was the night guard before going crazy and Murdering his wife. He then kills his youngest son. He then dies inside a Spring Bonnie suit.In night 6 he apparently kills the night guard.
After beating 10/20 mode you see a Spring Bonnie suit twitching. It's confirmed that William afton is inside the suit.