Onslow County, N.C., District Attorney Dewey Hudson told CNN he was shown "strongly compelling evidence" by the FBI Cpl. Cesar Laurean had gone south of the border sometime after Lance Cpl. Maria Lauterbach was killed last month.
However, Hudson said if Laurean is found in Mexico, he would have had "no other option" but to take the death penalty out of consideration since Mexico has repeatedly has refused to extradite suspects who could face capital punishment.
The semi-charred remains of Lauterbach and her baby were found in a fire pit behind Laurean's home Jan. 11, nearly a month after she was last seen.
Last year, she had accused Laurean of raping her, and was to have testified in a military court against him last month, the report said.