(CNN) Police say they have a confession from a Texas Border Patrol agent they suspect of being a serial killer, but many loose ends and questions remain -- chiefly, whether prosecutors will seek the death penalty.

It could take as long as 90 days to determine whether prosecutors will pursue capital murder charges against Juan David Ortiz, 35, accused of killing four women in and around the border town of Laredo, Texas, Webb County District Attorney Isidro Alaniz said during a Monday news conference.

Another loose end: Are there more victims?

Melissa Ramirez, 29, was the first victim linked to Juan David Ortiz, police say.

Asked by a reporter if he was certain they had identified all of Ortiz's victims, Chief Deputy Federico Garza of the Webb County Sheriff's Office replied, "We're not confident (of) that, sir."

He added, "We will do historical research everywhere that he has been to see if we have a pattern of victims."

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