Nancy Guthrie Update: Former FBI Agent Shares New Theory on Disappearance

It has been exactly three weeks since Nancy Guthrie was reported missing. Law enforcement continues to pursue thousands of leads in the search for the 84-year-old Tucson, Arizona resident, who is presumed kidnapped.

Authorities have struggled to come up with a motive for someone abducting Guthrie. Now, a former FBI agent has shared his own possible theory on what motivated the suspected perpetrator.

'Personal grievance' a possibility

Jonny Grusing, a 25-year veteran of the FBI's Denver Division...