Andrew "Andy" Hoffman was a former Staff Sergeant in the United States Marine Corps and also a serial killer responsible for the deaths of four women.
NCIS Season 5
Hoffman's M.O. was to head to a bar where he targeted his victims, the majority of whom were female military wives, presumably due to the fact that Hoffman himself was a former Marine.
After meeting them, Hoffman would get his female victims drunk and eventually unconscious by secretly lacing the drinks he had brought for them with Rohypnol.
Once they were unconscious, Hoffman would bring them back home and ultimately kill them by stabbing them, possibly in the chest with a knife.
After they had died, Massey would then cut off their left ring fingers and keep them as trophies, all for the sake of relieving the rush of the kill.