A satellite dramatically breaking up as it re-enters the Earth’s atmosphere.
 And it’s even been identified: it was the Cygnus mass simulator,
 a payload lofted into space by the Antares rocket in April!
On Thursday night local time (Friday morning, May 10 at about 01:00 UTC), the Cygnus dummy payload dropped down enough to experience re-entry.

http://www.slate.com/blogs/bad_astronomy/2013/04/17/antares_new_rocket_from_orbital_sciences_corporation_ready_to_launch.html

http://satobs.org/seesat/May-2013/0104.html

http://www.slate.com/blogs/bad_astronomy/2013/05/11/video_satellite_re_entry_looks_like_ufos_over_south_america.html