CNN PRODUCER NOTE Than Ball says he shot this video Thursday, September 12, 2013, showing sirens going off and floodwaters rushing. He says he got a warning text from the University of Colorado, where he is a student. It warned of a 'wall of water' and advised students to 'stay away from Boulder Creek' and "seek higher ground immediately.' He then heard sirens going off, which he happened to capture on video. 'And about a minute after I got that text message the flood sirens went off and people started clearing out of the area. Then about a minute after the video ends, police, firetrucks, and ambulances started showing up and evacuating people from the area while the sirens and warning announcements were still going off. It definitely took me by surprise that the flood sirens went off because they had sounded them last night, but it was such light rain while I was at the creek that I didn't expect to hear them go off at that moment.'
- nsaidi, CNN iReport producer