Mack's radio call sign of Dirt Diver is probably the most accurate of all the Alpha Team members, in that he is portrayed as a deeply flawed but intense warrior. He is frequently a hair's breath from losing it and is the closest among the team to being a villain. Not coincidentally, his wife Tiffy is the most flawed of the wives on the base.Gerhardt is a former Army Ranger who served with the 101st Airborne Division and 1st Ranger Battalion prior to joining the Unit. He is now the assistant team leader of Sgt. Major Jonas Blane's Alpha Team of the 1st Special Actions Group (official cover as the 303rd Logistical Studies Group ). He is competent in Italian and German and can fake both an Australian and Irish accent. While he is competent at submarine lock in/lock-out procedures he is slightly claustrophobic, which seems to be his only weakness. Like Jonas, he uses a customized Colt 45 as his sidearm. He is obviously a fan of the weapon, complimenting Bridget Sullivan for using one and recommending another new member of the team do the same. His off-duty gun is a Colt .32 pistol and he has a Smith&Wesson .38 throwaway gun. He and Tiffy have two daughters, Jen and Lissy.Mack appears to enjoy hunting off-duty and often wears a Triumph brand motorcycle T-shirt, although he is never seen riding one.