Kurt Hergis, who had been living in Costa Rica for eight months, was intercepted by four men Sunday night as he was returning to his home in San Carlos, a woman accompanying him told police.
His companion, who was identified by policy only by her first name Martha, said the men pulled Hergis out of his pick-up truck, hit him in the head, stabbed him and cut his throat.
She said she survived by begging for her life, police said.
The motive for the crime was not immediately known.
The local press said the assailants were driving a luxury vehicle in an area frequented by drug traffickers.