Mike Beers is a man who appeared in Grounded (episode). An airport security officer, he was supposed to depart for France.
However, a look-alike entered his motel room just as he was about to depart and shot him with a silenced gun before disguising himself as him.
The imposter needed to pose as him to deliver a gun to an assassin at the airport as part of a job against Hector Gomez, a Drug lord who offered a plea deal and was in transit to Dulles Airport, which was under a severe blizzard. NCIS Special Agents Eleanor Bishop and Anthony DiNozzo (who were at the airport preparing to go out of town with her husband Jake Malloy and waiting for the arrival of his father, respectively) grew suspicious of "Mike Beers" due to his behaving suspiciously, and eventually discovered that he was killed in a bathroom, also learning from the rest of the MCRT members that they had discovered the real Mike Beers dead in his motel room.