Rooker was the radioman of the Marine Raiders rescue team led by Sgt. Tom Sullivan and Cpl. Roebuck, which made a raid on Makin and saved Pvt. C. Miller. Later during the assault, the squad met a bunch of "dead" Imperial Japanese soldiers in the jungle. Sergeant Sullivan told Rooker to call another squad with his radio, in order to check if they already cleared that area.
When Rooker was going to use his radio, a signal flare rose, blinding everyone. Rooker is then stabbed by a Japanese soldier wielding a katana. However, Pvt. Livingston or Cpl. Lozano sacrifice themselves for Rooker if they have survived up until this point. His weapon in "Semper Fi" is an M1 Thompson.