Andre Turner, 48, opened fire on supervisors at his place of work on Friday, killing 56-year-old Henry Serrano of Walnut and 53-year-old Robert Lindsay of Chino. Both worked in the information technology division at Edison.
Turner also shot and injured Angela Alvarez, 46, an Edison employee, and Abhay Pimpale, 38, an independent contractor. Pimpale is out of the hospital, while Alvarez remains in critical condition.
On the 911 call, a caller tells the operator that gunshots are being fired.
"There are gunshots occurring outside the facility in the parking lot," the caller says.
"Who is firing?" the operator asked.
"We don't know," he says.
The Irwindale office was closed Monday, and flags were at half staff at all Edison buildings to remember the victims of the senseless tragedy.
"Our focus right now and continues to be on the families and the victims, trying to help them every step of the way during this very, very difficult time," said Steve Conroy of Southern California Edison.
Investigators are still trying to determine a motive.
More than 250 people turned out for a memorial service on Sunday to remember those lost in the tragedy, including family of the victims.
"We're like a family. We're all grieving," said Lois Pitter Bruce, an SCE employee. "There is no happiness for us. No matter how much you explain it, you can't understand it."