You have free will and are responsible for your acts. One is free to attribute some blame to the devil - credit where credit's due - but the consequences still fall in one's own lap; you could have said No to whatever Satan "made" you do. Credit where credit's due, but some evangelicals will attribute even a stubbed toe or burnt toast to the Evil One - a bit much. Certainly the impulse to kill a bunch of teenage xians ("the future leaders of our country", etc) could have Satanic origin.