Mission 94 – Kill Gaston's Enforcers
Lester Terriot. The info screen doesn't specify if his nickname is 'The Terrier,' but I think it's safe to assume that it is. His text box hints at an underground tunnel here, but it's not available to you. There is a back door to the garage at the north, but it's pretty crowded.
Unless you're looking for immediate chaos, sneak up the alley from the south east. You can lure a couple guards, then silencer-kill the rest. Just keep count of the remaining guards so you don't find yourself flanked.
After that, grab cash, destroy Targets of Opportunity and move out.