Supt. Eli Litman, head of the special inquiry team set up by the Amakim district, said there was no doubt that the suspect had killed the couple "simply because they were Jews."
Aghbariya told police he had acted alone, although investigators said they were not convinced that this was the case.
The suspect maintained that he did not belong to Hamas or any other terrorist organization, although it was later revealed that he was a member of the fundamentalist Israeli Arab Islamic Movement.
Aghbariya, 20, at first claimed that, on the day of the murders, he had felt oppressed because of personal problems and wanted to kill somebody. He allegedly armed himself with at least one knife and went to the northern Israel forest with that intention, he claimed.
Later, he altered his story and admitted that his intention had been to kill Jews, according to police.
Aghbariya reportedly first attacked Finfeter, 25, with a knife and stabbed him several times in front of his girlfriend, Steinmetz, 21, who tried to run away. But he caught her, and then allegedly hit her with a rock before stabbing her to death.