It's Lefty that became violent, not the Puppet.

YES! I KNEW IT! LEFTY IS NOT THE PUPPET! Cuz, I've been hearing a lot of people, especially those of the Gacha FNaF community say "Oh Lefty is Puppet, tẖ̷̨͇̋û̵̘̱̑s̴̬͎̰̜̈ ̷̬̇́̈̄̀s̸͓͕̦̓h̴̨̟̰̤̎̐́̒e̶̡͕̗̳̋ ̸̧͓͖̍́̕ͅš̷̭̗͇̗͌͂͠͠h̸͚̗̍̉̓̌͝ó̶͓̓u̵̧̫̹̜̅͗l̷͍̄̓̇̽̀d̴̙͈͍͎͊͠ ̶̦̭̈͘b̴̬͕̺̤̮̈́̎̍͊͗è̶͓́́̆͠ ̷̬̟̆̃̆s̸͕̗̘͘h̶̟̱̘̖̿̈́̋̀̀i̷̺̙̖͠p̷͕͉̥͎̀p̸͕̬̪͐͗̑ȇ̴̩͈̤͊͆d̴̛̞̭͊̿ ̷̨̗͈̼̻̀̇̓͘ẁ̶̮̟̑̚ͅi̴̠͉̠̎ͅt̵̥͉̜̀̾͛̕h̷̨̀͆̍̈́̅͜ ̷̙̮͋̌̀̐ț̸͊̅͂͜h̵̩̞͛e̵͍̅̅̿̆ ̸̛̦͖̃̓̓̿e̸͎̎̿͝x̶̝̍́͊̌a̴̙͎̩̔̋͒̃̏ͅc̸̣̝̰̙͉̈́̌̎t̷̙̋̉ ̷̛͓͎̗̈͒p̶̙̬͋e̷̪͊͊̈́̅ṙ̵̢̳̖s̵̬̖̑̿o̵͎̗̍̎͐̂͘n̸̛͕̈́ ̸̢̩̪͕̲͆̒ț̸̛̼̱̰̊̅͠ẖ̶̲͖̱̆̋͘a̶̭̺̤̍̾͆ͅț̸̟̙̓̀ ̶̯̪̬̗̞̈́̊̚ķ̶͔̜̤̫͑̋̀̍̚ï̷̢̧͓l̶̘̣̥̈́̽͌͝l̴̻͚̅͊͗͘͘é̵͎̅̔̉͒ḏ̸͗͜͝ ̸̳̺̜͇̱͂̊̒̄͘ḧ̵̫͕̪̭̎͐̅͘ḙ̷̄r̴̭͂̿̈͛̀"̵̵̵̵̵̵̵̣͉̭̼̣͉̭̼̣͉̭̼̣͉̭̼̣͉̭̼̣͉̭̼̣͉̭̋̒̃͂̋̒̃͂̋̒̃͂̋̒̃͂̋̒̃͂̋̒̃͂̋̒̃͂." Thank you for calling this out, Lefty isn't the Puppet, he is just an animatronic used by Henry to capture the Puppet.