A shooting at a Maryland warehouse has claimed four lives, including a female suspect who shot herself in the head, authorities said.

The suspect was a 26-year-old temporary employee at the Rite Aid distribution centre in north-eastern Maryland, Harford County Sheriff Jeffrey Gahler told a news conference.

She had been taken into custody in critical condition that morning. Her name was not immediately released.

Three other wounded people were being treated at a hospital.

Maryland Shooting
Authorities respond tothe shooting (Jerry Jackson/AP)

It appears only one weapon, a handgun, was used and no shots were fired by responding law enforcement officers, Mr Gahler said.

Krystal Watson, 33, said her husband, Eric, works at the facility and told her that the shooter was a female co-worker.

Ms Watson said her husband told her that the woman had been arguing with somebody else near a time clock after a “Town Hall meeting”.

“And she went off,” she said.

Ms Watson said her husband told her the shooting started in a break room.

“She didn’t have a particular target. She was just shooting,” she said as she drove away from a fire station where relatives tried to reunite with loved ones.

“She didn’t aim. She just shot,” Watson said.

A Baltimore hospital said it had received four patients with gunshot wounds from the shooting.

Johns Hopkins Bayview Medical Centre spokeswoman Monica Stone said in an email Thursday that she was unable to provide details about the patients’ conditions.

Mr Gahler said the call about shots fired came in from the Rite Aid distribution centre at about 9:06am
and deputies and other officers were on the scene in just over five minutes.

Mike Carre, an employee of a furniture logistics operation next to the distribution centre where the violence erupted, says he helped tend to a wounded man.

Mr Carre locked the doors of his workplace after the injured man came hobbling in, bleeding from his leg.

He called 911 from a bathroom before helping colleagues wrap the man’s blood-soaked jeans above his injury to cut off blood flow.

At a nearby fire station, family members were waiting to be reunited with loved ones. Police blocked off the road outside but were waving in cars driven by people who said they were there to meet up with people who were at the distribution centre.

A law enforcement official said authorities were working their way through the area to clear the facility.

“We obviously need to methodically go through the entire complex, ensure there are no other victims inside, ensure that there is no one that was hiding from violence and ensure that there were no other suspects,” said Christie Hopkins, communications director for the Harford County sheriff’s office.

“At this time, we are confident that the suspect acted alone. And that person is in custody. We do not believe there is any further threat to the community now, but we still have to completely clear that building.”

Maryland Shooting
Authorities respond to the shooting (Jerry Jackson/AP)

The attack came nearly three months after a man armed with a shotgun attacked a newspaper office in Annapolis, Maryland, killing five staff members. Authorities accused Jarrod W Ramos of attacking The Capital Gazette because of a longstanding grudge against the paper.

The FBI described the Aberdeen incident as an “active shooter situation” and said its Baltimore field office was assisting.

In a tweet, Maryland Gov Larry Hogan said his office is monitoring the situation in Aberdeen and that the state stands ready to offer any support.