Ford Focus problem!!?

Me and my dads friend drove our ford focus 2007 around for a few hours..came home and 30min later my dad tried to leave but the car wasnt completely dead..It wouldnt sputter and stop, or even begin to start. when i put the key in it made the little ding ding sound cause the car was open but other than that the lights are dead..and it wont start..could this be the battery?