After removing a stuck key from the ignition, it will not stay started?

So, the key to my car broke and it was stuck in the ignition. I told my boyfriend, but he forgot to get it out so the next day my battery had drained. So, he got key out hooked car up to the battery jumper it didn't want to start at first but then it did three times but shut off a couple seconds after. I plugged in my code reader but when I turned the key again all the lights inside the car were blinking and so was my code reader. I turned it off after that but tried to turn the key and had no lights or anything coming on. Scared to try again I'm not sure if it needs a new battery or why it would immediately shut off if it was absolutely fine yesterday and has half tank of gas.