The accused shooter fled the scene in a vehicle, with three Maryland State Police troopers giving chase after hearing an alert about the vehicle and seeing it, according to Lt. Col. Bill Dofflemyer of Maryland State Police.

The suspect fired at the troopers, who fired back, hitting the suspect, Dofflemyer said. A police press release said the suspect fired "multiple rounds" at the troopers, hitting one of them. At least one trooper fired back, hitting the suspect, the press release said.

They were taken to Meritus Medical Center for treatment. Dofflemyer said the trooper who was shot is doing well. Police said in a press release that the trooper was treated at Meritus, then released.

The press release said the trooper, who was not named, is a 25-year veteran of the department assigned to the Criminal Enforcement Division Western Region.

Police did not identify the accused shooter by name because he had not been charged yet. They described him as a 23-year-old West Virginia man.

He used a semiautomatic handgun in the shootings, Washington County Sheriff Doug Mullendore said.

Police said the man and the four victims worked at Columbia Machine Inc., a concrete products equipment manufacturing business at 12912 Bikle Road near Smithsburg.

The three people who were shot and killed at the business were Mark Alan Frey, 50; Charles Edward Minnick Jr., 31; and Joshua Robert Wallace, 30. Police did not provide their hometowns.

All three victims who died were found inside the business.

The fourth person who was shot — Brandon Chase Michael, 42 — was found in a nearby field by Smithsburg Police, the first police agency on the scene. Michael was being treated for his injuries at Meritus.

Police said the exchange of gunfire between the suspect and the troopers happened in the area of Mapleville and Mount Aetna roads, around where troopers first noticed the vehicle based on the alert they heard. The police press release said the troopers encountered the suspect about 15 minutes after the shooting occurred.

After the suspect was shot, police said, they found a handgun in the suspect’s vehicle, Dofflemyer said.

The initial police response to the shooting was at about 2:30 p.m. on Thursday.

State Police said the troopers who were involved in the shooting will be placed on administrative duty during an investigation.

The Washington County Sheriff's Office will investigate the homicides at Columbia Machine, with help from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

During a news conference on another topic on Thursday, Gov. Larry Hogan said: “The state police responded, pursued the suspect, suspect fired and shot the state trooper in the shoulder, who then returned fire and shot him back.”

Meritus Medical Center in Hagerstown, about seven miles from Smithsburg, was on lockdown from about 3:50 to 6:15 p.m., spokeswoman Michelle Lovelace said.

No patients, visitors or staff were allowed to leave the medical center during the lockdown and only patients experiencing a medical emergency could enter, Lovelace wrote in an email.

Government officials were among those who attended a media briefing following the shooting.

State Del. Neil Parrott, a Washington County Republican, called the incident “very surprising”.

But the community is tight knit and will act as a support system, he said.

“With the nature of this community, they will wrap around each other, help each other ...,” he said.

State Sen. Paul Corderman, a Republican who also represents Washington County, said accountability and responsibility are often missing throughout the country.

“When violent individuals commit violent acts, we need to hold those individuals accountable for those acts,” he said.

U.S. Rep. David Trone, a Democrat who represents the Sixth Congressional District, which includes Smithsburg, said in a phone interview that his office began receiving calls Thursday afternoon from people in the area, and he spoke with Smithsburg Mayor Donald Souders.

The incident appears to be a “workplace type situation,” and it wasn’t clear Thursday evening what type of weapon was used, Trone said.

He said his thoughts were with the families of the three people who were killed, as well as those who were wounded.

”We pray that [they] recover so [the suspect] can be held to justice,” Trone said.

Trone said every member of Congress feels like it’s only a matter of time until this happens in their district.

He met with Senate Majority Leader Chuck Schumer on another matter Wednesday, and said it appears the Senate is putting together a bill to help keep people with mental health problems from getting guns.

A lifelong hunter, Trone said Congress needs to act to control the sales of assault weapons like the AR-15 rifle.

”That’s not a hunting weapon. That’s not a sport weapon,” he said.

But Trone said lawmakers need to do more.

”Thoughts and prayers are not enough,” he said.

“I’m devastated by the lives taken today in Smithsburg and for the pain and suffering their loved ones are experiencing,” U.S. Sen. Chris Van Hollen, a Maryland Democrat, said in a statement. “Today’s horrific shooting comes as our state and nation have witnessed tragedy after tragedy, and it’s got to stop.

”We must act to address the mass shootings and the daily toll of gun violence on our communities. ... I am committed to meeting your pain with action.

“A horrible tragedy has taken place in Smithsburg,” U.S. Sen. Ben Cardin, a Maryland Democrat, said in a statement. “My thoughts are with all of the families of the victims today. This cannot keep happening.”

In a statement, Meritus Health President and CEO Dr. Maulik Joshi said: "Tonight, our hearts are heavy as we grieve with our community."

Staff writers Ryan Marshall and Mary Grace Keller contributed to this story.