WASHINGTON (AP) — Ex-CIA director David Petraeus has told friends he was shocked to find that his biographer and girlfriend, Paula Broadwell, was suspected of sending anonymous, threatening emails to a Petraeus friend she saw as a romantic rival.

A close Petraeus associate said Monday that FBI investigators told Petraeus that Broadwell sent anonymous emails to Jill Kelley, a Petraeus family friend from his time at Central Command in Tampa, warning her to stay away from him. The Petraeus associate spoke on condition of anonymity to discuss confidential conversations with Petraeus. The CIA director resigned last week after confessing to the affair.

Petraeus was not shown the emails, but was told the tone and content seemed threatening to Kelley, prompting her to report them, the close Petraeus associate said. That triggered the investigation that led the FBI to Broadwell and evidence of her affair with Petraeus.