Numb3rs Fanfic Finders

Quite a while ago I read a fic where Don was looking into a case where someone was killing off fbi agents and then, during the case, charlie spotted someone watching don and david at their home
since don fit the bill more they assumed he was after don and they wanted to set a trap for the killer using don as bait, charlie disliked it but was overridden
the killer kidnapped charlie at some point along with the agent guarding him who was her next target, charlie is there while hes killed and then left alive but the warning is not to get him more involved
in the end it turns out that don is one of the intended victims after all and he is taken to calsci where she starts to kill him before charlie shows up

the killing method was brutal as she cut them open in the chest and removed the heart while still alive because they had betrayed her romantically, or so she believed
she used to work at quantico before being investigated and thrown out