Gary Buser was one of many low-level thugs hired by Grant Ward and Gideon Malick to join their newly-forged, individual branch of HYDRA, and was subsequently given a cybernetic power-armor that was donated to Malick's HYDRA by AIM, who were under orders by Andrew Forson. The armor was based on the iconography of a snapping turtle on the basis that he would be the hard exterior shell protecting HYDRA's already fragile interior from S.H.I.E.L.D. In addition to the armor Gary received a weapon capable of launching a wide variety of projectiles. After Gary was equipped with the armor he then went by the alias Shellshock.
Shellshock uses a special handgun that fires assorted projectiles, including explosive projectiles, heat-seeking and guided projectiles, and an expanding yeast-putty which entangled opponents.