My group killed the middle guy last and the chest was locked, which was a lil frustrating, since we were all eager for the biometric crafting material as well as the loot.
we've since done this encounter with a variety of ways of killing (altho we never kill the left guy last). Never once has the chest been lootable (granted, only 3 kills so far)
edit: forgot to put point of killing differant ways
Rumor is if you one shot the encounter and do not wipe.. the chest opens.