I saw it first very rapidly moving across the sky, then it looked like an explosion that created a still bright but more diffuse light source (probably 20x the size of the original bright flash traveling across the sky; it looked like some parts of the diffuse cloud of light were brighter than others with a dip in brightness in the center-bottom area - could be fragmentation post explosion?). The diffuse cloud then swirled for a while (~20-30 seconds) and sunk down below the building in front of me so I couldn't see it in the sky anymore and track how long it lasted
