Harford County, Maryland, Sheriff Jeffrey Gahler said Prince shot his victims and fled the Emmorton Business Park in Edgewood, eluding deputies who arrived in four minutes.

Kevin Doyle of Thornhill Properties said he was getting tools from his truck when he heard screaming and saw three men running from the office park. The men told him someone was shooting and he asked if they had called 911. They said no, even though, Doyle said, they had phones in their hands.

“I think they were just so scared, they didn’t (call 911). They had a look of terror,” he said.

“This does appear to be a targeted attack, limited to that business,” Gahler said as he confirmed there were three dead and two other victims who were transported to trauma centres in serious condition.

Police were investigating Prince’s connection with the business, known as Advanced Granite Solutions. All five victims were employees of the business, Gahler said.

The victims and the suspect worked for Advanced Granite Solutions, the owner of the company that designs and installs worktops. Prince has been an employee for four months, working as a machine operator, owner Barak Caba said in a brief telephone interview. Caba was shaken and would not provide additional details.

The wounded were in critical condition with gunshot wounds to the head, according to Maryland Governor Larry Hogan, who spoke at an unrelated event.

He said authorities in helicopters and on the ground were searching for Prince, who may be driving a black 2008 GMC Acadia with the Delaware license tag PC64273.

“The killer remains on the loose,” Hogan said.

The shooting took place just weeks from October 1 when a gunman in an upper-floor casino hotel room opened fire on concertgoers in Las Vegas, killing 58 and wounding more than 500 in the deadliest shooting in recent US history.

To date in 2017 there have been 285 mass shootings – defined as four or more people shot or killed, not including the gunman – in the United States, or nearly one per day.

Prince was fired from another job earlier this year after he attacked a colleague, according to The Baltimore Sun. A former colleague sought a restraining order against Prince in February, saying he had punched another employee and threatened employees.

“I felt very threatened because he is a big guy and very aggressive on me,” the colleague said in the application for the restraining order. The man said Prince did not get physical with him, but wrote: “I do not want to wait until he will.”

A Harford County District Court judge denied the order. The newspaper article did not identify the business or colleague.

The FBI is assisting local authorities. Investigators were treating the shooting as a case of workplace violence and didn’t see ties to terrorism, said Dave Fitz, a spokesman for the Baltimore FBI field office.

Variety magazine reported that the set of “House of Cards,” which is partly filmed in Maryland, was placed on lockdown while police searched for the gunman.

The executive producer of the series, Dana Brunetti, addressed the incident in a Facebook post, and criticised cable networks for not immediately reporting it.

“Shooting near House of Cards set,” Brunetti wrote. “I turn on the news to see what is happening, and guess what they’re covering? Not the 5 dead and 3 wounded while gunman is still on the loose.”

Some of the school lockdowns were later lifted, according to Harford County Public Schools.

The incident was the latest mass shooting in a country where such killings have become commonplace.

There was heavy police presence along Interstate 95 in Maryland and Delaware. Cruisers were stationed in medians, and overhead highway signs displayed a description of Prince’s sport utility vehicle and its Delaware number plate.

According to online court records, Prince lived in Elkton – about 35 miles (56 kilometres) from the shooting scene – as recently as last month. He faced several gun charges in March 2015 in Cecil County, including being a felon in possession of a firearm and carrying a handgun in vehicle. However, the charges were dropped about three months later.

A Maryland property manager said Prince often paid his rent late, but was always polite and cooperative. Heather Todd said Prince has rented a three-bedroom town house since November 2014 and lives there with his girlfriend. Her company, Homes for Rent, has filed eight petitions for non-payment of rent against the couple. But she said they always ended up paying their rent and the company never had to schedule an eviction.

The sheriff said authorities checked an Elkton home after the shooting, but Prince was not there.

Wilmington, Delaware, police said he had relatives in the area there. Police spokeswoman Stephanie Castellani said the victim at the used car lot is best described as an “associate.” She said the shooting “was not a random act.”