why did my snake bite me?

I have two ball pythons one female one male, both about 4-5 months old, the female isn't aggressive at all and is quite curious. the male is aggressive when he is shedding, and kind of hides his face a lot and seems to be quite shy, I have them in a 55gallon terrarium with a 75w night bulb that stays on all day and night, and then white bulb 60w bulb that's on only through out the day time. and I have a under tank heater on the same side of the tank that the lights are on, so I have one cooler dark side with wet moss hides and a warm bright side with the large water dish where both of them soak on a daily basis and rock cave over the heater also the heater is part way under the water dish so it helps keep the water warm since it is winter and helps with the humidity. I feed them a live regular size mouse ever 6-7 days I tried feeding the male a frozen the other day and he went towards the mouse which I was holding by my hand and not tongs (stupid rookie mistake, I couldn't find them at the moment), anyways he went towards the mouse then struck around the mouse biting the palm of my hand. did he just mistake my hand for the mouse or was he threatened by me for some reason?, I did just feed them a few days before I tried with frozen, but just wanted to give frozen thawed mice a try since by milk snake eats them and it would save me some money and more convenient since Im having trouble breeding my own mice. please any advice on the reason he bit me or any other advice on the living conditions would help