Lieutenant Tomathren can be found in the Ghostlands, north of the Farstrider Enclave. He is found patrolling the campfire near Ranger Valanna. Tomathren was the leader of a poorly conceived attack on Zeb'Sora, and is not on the best of terms with her.
Also notable, is that the first line of text when you talk to him is "It's not my fault...IT'S NOT MY FAULT!!!". This is likely a reference to Leeroy Jenkins.