give the starter solenoid a good whack? then try again?
it sounds like either the battery isnt supplying the current, or the starter is sucking too much current.
maybe that the starter solenoid is on the way out?
may also be that you earthed something (for just a little while), and damaged the battery plates, meaning they cant provide enough curerent to crank?
if simply whacking the starter solenoid a few times with an extension bar and a hammer gets you nowhere, grab your dads battery, and try that.