Sins... easiest, if you don't have anything else... duct tape it so that you have a tab of tape to screw to the wall and use a washer or make one of wood. Best is a metal strap, screwed to the wall on both sides of the downspout. At the least, remove the free piece(s) to avoid damage until it can be fixed properly.

Same stuff here this morning... snow, sleet, rain, snow, sleet, rain...