Media playback is unsupported on your device Media caption Deputy Police Chief Kris Arneson said the gunman killed himself

A disgruntled former employee has shot dead four people at a sign-making office in Minneapolis before killing himself, police in the US state of Minnesota say.

Four people were injured, three seriously, in Thursday's shooting at the Accent Signage building in a residential area of the city.

The police said officers found the bodies inside the workplace upon arrival after multiple 911 calls.

The shooter was fired earlier that day.

The gunman, who died from a self-inflicted gunshot wound, was identified as Andrew Engeldinger, a 36-year-old from Minneapolis, said Police Chief Tim Dolan.

He returned to his former workplace at about 16:25 local time (21:25 GMT) and began shooting people.

But Chief Dolan added: "It's clear he did walk by some people, very clear."

'Horrible tragedy'

Among the victims was the company's owner, Reuven Rahamim.

In a statement his son-in-law, Chad Blumenfield, told the Associated Press that Rahamim had been an "incredibly proud husband, son, father and grandfather".

Image caption Police cordoned off the area after shooting

Accent Signage Systems makes interior signage, including in Braille. It reportedly employs nearly 30 people.

Police were called to the scene at about 16:30 local time after several calls from inside the business.

"When officers arrived and entered the business to assist with the evacuation of employees, give aid to the victims and to search for the suspect, they found four victims dead from apparent gunshot wounds," police spokesman Steve McCarty said in a statement.

Officers from several law enforcement agencies, including Swat teams, arrived in the area.

One woman told a local news station that an employee of Accent had hid in her home for 30 minutes.

"He was visibly fearful," Barb Gasterland told KARE11. "He came running up the side of the road and asked for the phone because he was running from the shooter."

About an hour into the incident, police reported the gunman had shot himself in the building's basement, the Minnepolis Star Tribune reported.

Mr McCarty said police had searched the house of the suspected gunman on late Thursday.

They found another gun and packaging for 10,000 rounds of ammunition inside. Chief Dolan said the gunman had "obviously been practicing in how to use that gun".

One of the critically injured, John Souter, was upgraded to serious on Friday, according to Christine Hill, a spokeswoman for the Hennepin County Medical Center. A fourth person not critically injured was treated and released.

Minneapolis Mayor RT Rybak called the shootings "a horrible tragedy", saying: "We are deeply sorry about what has happened here."

Minnesota Governor Mark Dayton expressed his condolences to the families and friends of the victims.

"I deplore this senseless violence. There is no place for it anywhere in Minnesota," Mr Dayton said.