SAN FRANCISCO (AP) — A UPS employee opened fire at a San Francisco package delivery facility on Wednesday, killing three employees and then himself as officers closed in, police and the company said.

San Francisco assistant police chief Toney Chaplin said a news conference that two others were wounded in the shooting that prompted a massive police response in downtown San Francisco.

READ MORE: Kelly Price, Well-Known Gospel And R&B Singer, Registered As Missing Person

Police have not determined a motive. Chaplin said that the shooter was armed with an assault pistol and put the weapon to his head and pulled the trigger when police found him.

A UPS statement said the shooter and all the victims were employees. Spokesman Steve Gaut told The Associated Press that the gunman opened fire inside the facility before the drivers were sent out for their daily deliveries.

Neighbors said they heard up to eight rapid gunshots.

“It was like tat, tat, tat, tat, tat, tat, tat,” said Raymond Deng, who lives across the street from the warehouse.

After the gunfire, auto shop owner Robert Kim said he saw “a mob of UPS drivers” running down the street screaming “shooter, shooter.”

READ MORE: Costco And Other Big Box Retailers Limiting Number Of Some Items Customers Can Purchase

Deng, 30, a data scientist for a start-up company, also saw workers fleeing and another group of about 10 who gathered on the roof and held their hands up as police arrived.

“I saw police officers go up from the ramp and then storm the buildings,” he said. “It’s crazy.”

Police responding to the facility in the Potrero Hill neighborhood, about 2 ½ miles from downtown San Francisco, found wounded victims and pulled them to safety. Then they found the gunman, who killed himself.

Investigators recovered two firearms from the scene.

Uniformed UPS employees were later led out in a line by officers next to a highway. They walked away calmly with emergency vehicles nearby and gathered nearby outside a restaurant.

It came the same day a gunman opened fire on Republican lawmakers at a congressional baseball practice, wounding U.S. Rep. Steve Scalise of Louisiana and several others.

MORE NEWS: Friday Last Day For LAUSD Employees To Get First COVID-19 Vaccine Dose Before Oct. 15 Deadline

(© Copyright 2017 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)