Your snake was striking defensively. You really need to let him settle in and he should be fed in his own enclosure. It sounds like you just stressed the hell out of your ball python. You should wait at least a week before trying again and don't be so hands on. Leave the mouse in the snake tank and just sit back and watch for 15 or 20 minutes. People try to "help" far too much and stress the snake out. Just my $.02...
Regards,
B