T-47 is not working properly

[Count.Rushmore]

T-47 Challenge Talk

I wanted to get T-47 (Berlin) silent assassin, so I started as a biker, grabbed the shotgun in the starting room, subdued targets and moved them right near body closets, shot them with the shotgun and hid the bodies really quickly before people investigated the gunshot, and I escaped using the bike, but the challenge didn’t pop. Do you have to not subdue the targets first or something?