An employee at a Rite Aid warehouse opened fire at work on Thursday, killing three people before taking her own life, authorities said. Several other people were wounded.

The suspect was a 26-year-old temporary employee at the Rite Aid distribution center in northeastern Maryland, Harford County Sheriff Jeffrey Gahler said at a news conference. The sheriff’s office said in a tweet a short time later that she had been identified as Snochia Moseley of Baltimore County.

Krystal Watson, 33, said her husband, Eric, works at the facility and told her that the suspect had been arguing with somebody else near a time clock after a "Town Hall meeting."

"And she went off," she said.

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

"She didn’t aim. She just shot," Mrs Watson added .

Local hospitals reported receiving five patients from the incident.

Johns Hopkins Bayview Medical Centre in Baltimore said it was treating four patients with gunshot wounds. Two were in stable condition and two who were seriously injured.

A spokesman for a health system that includes Christiana Hospital in Newark, Delaware, said one patient was being treated there. Christiana Care Health System spokesman Hiran Ratnayake said the person was in serious condition.

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

He said the suspect had reported for the work day as usual, and around 9 am the shooting began outside the business and continued inside.

The shooter had two or maybe three magazines for the gun. He did not know how many shots were fired.

Mike Carre, an employee of a furniture logistics operation next to the distribution center, said 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.

Mr Carre said the man told him the shooter "just came in in a bad mood this morning. He said she’s usually nice. But today, I guess it wasn’t her day. She just came in to pick a fight with someone."

"She pulled out a gun and she just started shooting at her co-workers."

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

Reggie Rodgriguez’s mother works at the distribution center. His wife had tried calling her numerous times but got no answer.

"I was calling her all morning. It went to voicemail because they keep their phones in lockers," said Kelly Rodriguez, 40.

When they finally reached his mother Thursday afternoon, Reggie Rodriguez said, "That’s all I wanted to do: Hear her voice." His mother was uninjured. He said she sounded relieved the crisis was over.

A law enforcement official said authorities worked their way through the distribution centre to clear the facility.

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 Ramos of attacking The Capital Gazette because of a longstanding grudge against the paper.

Susan Henderson, spokesman for the drugstore chain Rite Aid, described the warehouse as a support facility adjacent to a larger building.

Harford County Executive Barry Glassman said that unfortunately, incidents like this are "becoming a too-often occurrence not only in Harford County but in the country."