Autism?
Epilepsy?
Partial incapacitation?
Halucinatory reaction due to taking undeclared anti depressants ?
All of the above assuming there is coherent evidence P1 was indeed locked out and that he was indeed the one banging at the door.
Does German Wings really not practice 2 crew seated in the cockpit policy? Due to operating with mininal cabin crew? Low cost driven?
How about now imlenenting cockpit CTV and an Emergency Door release policy that each cabin crew can access via SATCOM from their communucation panel to Security Chief?