First Against the Wall Trophy

[whoareyouiamme]

Hello!

 

This trophy is the only one I need before I can get platinum.  I found a great spot where I round a corner and there's 2 security guards in envirosuits and 90% of the time, one of them will audibly surrender with "mercy please" or another cowardly catchphrase and then go cower.  I've killed them so many times as they retreat to go cower after saying a line, but this trophy will not pop for me.  I keep reloading the save, but this trophy will not pop. 

Does anyone have any ideas or am I missing something?  Does this trophy not work with save scumming?