Mark Devlin

Agent Mark Devlin was a member of a rogue NID operation which would eventually become The Trust.

He tried to assassinate Senator Kinsey but was unsuccessful. After SG-1 started investigating the crime, he tried to assassinate Kinsey a second time (Disguised as Maj. Davis) but was stopped before he could pull the trigger.

Somewhere in-between this and reporting back to "the Committee", he is either killed or captured by SG-1 and Major Carter uses an Area 51 engineered device in order to mimic Devlin.