A postal worker has shot and killed three people before turning the gun on himself at a San Francisco depot, local media report.

United Parcel Service (UPS) spokesman Steve Gaut said an employee opened fire on colleagues before drivers were sent out for deliveries.

The suspect shot himself when confronted by police and later died in hospital, NBC7 and ABC7 reported.

Police said the building was secure but did not offer details on the victims.

“UPS confirms there was an incident involving employees within the company’s facility in San Francisco earlier this morning,” the company said in a statement on Wednesday.

“We cannot provide information as to the identity of persons involved at this time, pending the police investigation.”