Mandy Moore "Heartbroken" Over DJ AM's Death

Friends, family and fans will be mourning the death of DJ AM for weeks to come, but one person specifically is having a hard time accepting that he's gone.

AM's ex girlfriend Mandy Moore is speaking out about her loss and how heartbroken she is.

"I am absolutely heartbroken," she said in a statement to Us Weekly about her ex. "For those of us lucky enough to have known him, Adam radiated a contagious exuberance for life and also personified the very definition of a true friend."

"To say that he will be missed beyond words is an understatement," she continued. "My heart goes out to his loved ones."

AM also dated Nicole Richie a few years, but we've yet to hear anything from her or her camp.

AM was found dead in his New York apartment Friday afternoon and investigators believe an accidental overdose is the cause of death.