Lachlan McDermott

"He looks just like his father. Makes me sick!"

Lachlan McDermott was an accomplice of Chloe Donaghy.

Background
Not much is revealed about McDermott's background besides the fact that he is apparently born and raised in Ireland and that his family, the McDermotts, has been in a long family feud with that of international terrorist Ian Doyle. He killed Lachlan's older brother, Jimmy McDermott, in Dublin by stabbing him and slashing his throat, leading to Lachlan wanting to avenge his brother's death. At some point, he moved to the U.S. and got hold of some warehouses in Baltimore, Maryland and used them as part of an "import company" he founded, presumably to use as cover for criminal operations. In 2011, he was contacted by Chloe Donaghy, a former lover of Doyle, who recruited him and another enemy of Doyle's, a low-level gun-runner named Richard Gerace, for an operation to kidnap Doyle's son, Declan, and extract ransom money from him.

It Takes a Village
After somehow tracking down Declan to his boarding school in Virginia, Chloe goes there and serves him and some other students tainted cupcakes, causing Declan to suffer food poisoning and be sent home. At night, McDermott and Chloe break into the house, having Gerace disable pole cameras set up by Morgan earlier, and kill two FBI agents sent to the house and also Declan's nanny, who is brutally beaten to death by Chloe. They take Declan to one of McDermott's warehouse, where one of them later kills Gerace with a shot to the forehead. They then head for an airfield to which McDermott's family previously has imported weapons and board a jet, planning to leave the country with Declan. On the plane, McDermott voices his frustration that they couldn't bring Doyle out of hiding before the FBI caught him, though he is willing to settle for Declan, whom Doyle will inevitably try to track down. As the plane is about to take off, the BAU arrive with Doyle in custody, offering to trade him for Declan. McDermott is more than willing to make the deal, but Chloe, who was in it for the money, tries to stop him and is shot in the chest. As McDermott leads out Declan to the air strip, Chloe staggers out of the plane, shoots Doyle and McDermott to death and is shot herself.

Modus Operandi
McDermott killed his victims either by shooting them or beating them.

Known Victims

 * Presumably several other crimes prior to It Takes a Village
 * The attack on Declan's home:
 * Two unnamed FBI agents
 * Declan Doyle
 * Richard Gerace
 * The airfield shootout:
 * Chloe Donaghy