At the start of Chapter 8, talk to Tannis to start this mission. Next, head to Moxxi's place and get the pizza there as bait. Next, use a fast-travel station to travel back to the Bloodshot Stronghold. Continue until you find the marker. Jump down to the lower level and go through the tunnel.
Kill the next few enemies until you find a room with an intercom. Activate it and place the pizza on the table in the middle. Four enemies will appear one by one, so keep moving and kill them all. These guys are very mobile so use shotguns, SMGs or assault rifles to take them out.