A excess of firepower can be used to solve any social, economic, or military situation. Also, Wraiths rule!
I have found (and for some, killed) 5 Bobs on different levels, but I only have screenshots for 4 of them. They are as follows:
Nightfall, Normal- Bob at the militiamen's pumping plant, I failed to kill it before it despawned. Screenshot in File Share.
Tip of the Spear, Not Sure- Aggressive Bob with a fuel rod gun, just after the falcon crashes. Killed it. Screenshot in File Share.
Long Night of Solace, Normal- Bob in the control room, not sure if it was aggressive or not. Killed it. Screenshot in File Share.
Long Night of Solace, Normal- Bob at teh Pelican Defend section, just as you walk into the room. Coundn't kill it. Screenshot in File Share.
The Pillar of Autmun, Heroic- Bob at the Vehicle Spwan area if it were Invasion. Didn't kill. No screenshot.
The screenshots are in my File Share if you want to confirm.