You just recently started playing the game, right? Continue playing, and he will get unlocked automatically at some point. I can’t remember at exactly which level he gets unlocked but it’s pretty early and then he’s the only purple officer you have for a while until you unlock a couple others. So just stick with it and he’ll become available soon just by playing the game. For this particular video though, it’s not the regular “Mercenary Survivor” levels in which you can only use the regular officers you’ve unlocked. It’s “Desperate Hunt” and they freely provide the purple officers for this, perhaps to entice people to pay money to unlock these officers for the “Mercenary Survivor” levels. As for me, I haven’t spent a dime on the game. What I’ve unlocked is just by playing the game without making any in-game purchases.

😂😂🤷🏻‍♂️