SAN FRANCISCO, June 15 (Xinhua) -- A gunman killed three co-workers before killing himself in a shooting spree Wednesday morning at a United Parcel Service (UPS) facility in San Francisco.
Police were probing the gunman's motive but did not believe it was linked to terrorism.
The incident took place before 9:00 a.m. local time (0200 GMT) at the UPS warehouse and customer service center in the Portero Hill neighborhood of the city on the U.S. West Coast.
Local media quoted witnesses within the warehouse as saying that the gunman went in through the front entrance and started shooting, without saying anything, once at the back of a victim and then at the heads of some others.
The shooter killed three co-workers and wounded two others before turning an assault pistol to his own head when police approached.
The gunman was identified by authorities as San Francisco resident Jimmy Lam. He was a driver for the package delivery company.
All of the victims were UPS drivers, and the incident occurred when they gathered for their daily morning meeting before starting their package deliveries, UPS officials said.
Lam filed a grievance in March complaining about the excessive overtime working and he appeared to target the three drivers who died, local union officials said.
The two other drivers who were wounded in the incident had been released from hospital, the officials said.
Assistant Chief Toney Chaplin of San Francisco Police Department (SFPD) said two guns were recovered from the facility.
Unconfirmed media reports based on a witness account said the gunman shot victims in an "execution-style," and at least one report alleged that Lam had "a history of mental illness."
About 850 people are employed at the site, the largest for UPS in San Francisco.
Witnesses said the shooter was wearing a UPS uniform, and Chaplin declined to identify those killed and injured.
Police treated the facility as a crime scene and put it on lockdown.
"At this point," Chaplin noted, "we do not believe this incident is related to terrorism."
Chaplin said police were interviewing families of victims and witnesses to determine the motive of the gunman. UPS said it is awaiting police investigation.
The San Francisco incident came three years after a UPS employee shot dead two of his supervisors before killing himself at a UPS distribution center in Birmingham, Alabama.
Police have not disclosed the identities of the victims killed. UPS is providing trauma and grief counseling to employees at the San Francisco center.
