Me and my sister broke the kitchen door window. Now we need an excuse for how it got broken !?

Well we were in the kitchen playing an we were by the kitchen door and her head hit the gl and broke.And its not like its a little broken, but half of the gl is broken. My mother always tells us don't play in the kitchen but we were. So what do we tell her happened. I was going to say that i tripped over the broom and it fell into the gl but the broom or the mop is not tall enough. Then I said well we can say that i was getting something from over there and my sister jumped out and scared me and my elbow hit the gl. But then my sister got scared and said was like we are going to get in trouble and i was like well we would get in more trouble if we say what we were really doing. So what should we say?