It happened Wednesday just after noon at The Home Depot on Azusa Avenue.
Witnesses say the man walked down an aisle, picked one a hand saw and started cutting his arms.
“He just began sawing away,” Lt. Rudy Lopez told The L.A. Times.
“He was pretty much intent on doing what he did.”
An employee saw what was happening and rushed to help the man.
People at the store, including an off-duty paramedic, were able to control the bleeding until help arrived.
He was taken to Queen of the Valley Medical Center where he underwent surgery.
There was no word on his condition. The store was closed for the rest of the day.
By Kennedy Ryan, KTLA