The identify of the whistleblower in the case of Charles Cullen, the serial killer nurse, has been revealed.
The New York Post reports that a new book "The Good Nurse" by Charles Graeber says investigators' confidential informant is Amy Loughren.
She's a nurse who worked with Cullen at New Jersey's Somerset Medical Center his last job.
The book says Loughren was a confidant of Cullen who noticed oddities in Cullen's drug orders and helped investigators with files and interrogations.
Cullen is serving life in prison for killing 29 patients in Pennsylvania and New Jersey.