A Southern California Edison employee chatted calmly with co-workers in the moments between gunning down four managers during a rampage at an office complex, authorities said as the building reopened Tuesday.
Investigators still were trying to determine what pushed gunman Andre Turner to finish a normal workday by shooting the workers with a semiautomatic handgun before turning it on himself.
"He gave no indication of what was going to occur later that day," homicide Lt. Holly Francisco said in a statement on the Sheriff's Department website.
"In between shooting different co-workers, the suspect calmly walked past several co-workers and had brief and calm conversations with them," Francisco added.
Turner, 48, a systems analyst, had been reprimanded for a mistake and court records indicate that he may have had financial problems.
Security was tightened at the reopened Irwindale office complex. Grief counselors were on hand at the facility east of Los Angeles that houses about 1,050 employees involved in Internet technology and electrical transmission and distribution.
It was unclear how many employees returned to work in the wake of Friday's attack.
"You really can't imagine what it's like to go through something like this," Edison spokesman David Song said. "The feeling of unbelief, and obviously sadness and sorrow. It's a big company but in a lot of ways it's ... tight-knit. A lot of people are only one person removed" from a victim.
Most employees were unaware of the attack while it was happening and some who heard gunshots did not realize what they were hearing, the lieutenant said.
The attack killed Robert Scott Lindsay, 53, of Chino Hills and Henry Serrano, 56, of Walnut, authorities said.
Angela Alvarez, 46, of Glendale, an Edison employee, and Abhay Pimpale, 38, of Montebello, a contract worker, were wounded.
Pimpale, the father of a 3-year-old son and a newborn baby, was released Saturday from a hospital.
Alvarez was upgraded from critical to serious condition at County-USC Hospital on Monday, spokeswoman Rosa Saca said.
All four victims had "some sort of supervisory role" at Edison but it was unclear whether they had any role over Turner, Francisco said.
Turner had been verbally reprimanded for missing an audit deadline but it was unclear exactly when that occurred, Francisco said.
He also may have been having financial problems.
The Press-Enterprise of Riverside has reported that Turner bought a 5,000 square-foot, five-bedroom house near Hidden Valley Golf Club for $711,000 when it was new in 2004 but put it up for sale in November for $590,000.
Court records indicate that Citibank was awarded more than $5,000 after the bank sued Turner in 2008 over credit card debt, the Los Angeles Times reported.
About the same amount was awarded to Cavalry Portfolio Services, a debt collection agency that sued Turner in 2009 on behalf of a credit card issuer, the newspaper said.