"Buck" Firefight Character - Complete "Tayari Plaza" on Normal or higher.
"Dare" Firefight Character - Complete the Campaign on Legendary difficulty.
"Dutch" Firefight Character - Complete "Uplift Reserve" on Normal or higher.
"Mickey" Firefight Character - Complete "Kizingo Boulevard" on Normal or higher.
"Romeo" Character - Complete "NMPD HQ" on Normal or higher.