That can sometimes be the result of a Bottom Bracket failing.
I have no experience of what type of BB is fitted to the Schwinn but cheaper BB bearings often have no cage...a ring inside that keeps the balls of the bearing apart from each other. What can happen is the balls touch and as the surfaces are rotating they can grind into each other, jam temporarily then the bang is as they almost bounce off each other with some force. It's not a brilliant description but that's happened to me a couple times on older bikes of mine . If the bang is Intermittent, perhaps more often when you pedal hard....id look at servicing the BB or replacing it.
If it is a new bike, is it under warranty, if it's really new the BB shouldn't have failed so soon.
It can be other things as well....a bit of time inspecting will help . Stand at the side of the bike and grab hold of the crank arm and see if there is any excess play or wobble, again this may indicate the BB is failing. Are the crank arms tight on the axle. ? Rotate the crank arms slowly by hand, can you feel the rotary action is smooth or does it feel like it's catching ?