Loud Boom Reported in Colorado Springs

Several hours post thunderstorm around 4:20 am I woke up to something that I thought was gunshots at first, but then thought was fireworks. Sharper and shorter than thunder but also echoing boom. Some in quick succession and other spread out by a few minutes. I am in Black Forest outside the city, but sounded like it was coming from closer to the city. Exact direction was hard to pinpoint but seemed southwest. Based on the way the valley echoes it could have been the opposite. Lasted at least ten-fifteen minutes (I woke at 4:20 but possibly started before). No visible lights, lightning or source and the sky looked mostly clear.