Combat Medic Archive

Before my venture into the combat medic field i saw a master apply an area of effect poison to a group ofwomprats without gaining agro. Once they were all fairly destroyed we one shotted them all avoiding any damage. I can't seem to replicate this tactic i get targeted instantly, whats the trick? Coupled with rifle its imperative to not let a mob close on me.

He probably has at least Scout 2000 and was using mask scent, and probably /peaced after tossing the first poison.