What if Heller himself is involved? He is the Secretary of Defense and one would think that in order to 'steal' 16 cannisters of nerve gas one would have to grease the right palms even if they are the President.
Heller confronts the Pres to try and cover his own butt but Jack discovers the connection and offs Heller. He's already tortured and killed Audrey's husband last season so why not her dad too?
Just more speculation
.