SUMMARY
The Sedra City Mall Bombing was a terrorist attack on the human colony world of Sedra in the Orrichon system by an unknown Sangheili terrorist organization in February 2556. The attack utilized a bio-weapon that only targeted specific humans, the source of which was discovered to be the remains of Installation 04 from after John-117 detonated the Pillar of Autumn's engines at the end of the Battle of Installation 04. A team of ONI agents led by Jameson Locke attempted to stop the attack, but they were unsuccessful.
RELATED MEDIA
These events are depicted in the movie Halo: Nightfall, which was the subject of several Spoilercast episodes in November and December 2014.