A woman armed with a handgun has opened fire at a US pharmacy distribution centre in Maryland, killing three people and wounding three others before taking her own life.
Thursday's shooting unfolded shortly after the suspect, a temporary employee, reported for work at the distribution centre for the Rite Aid chain about 9am (local time) in Perryman, Maryland, Harford County Sheriff Jeffrey Gahler told reporters.
The sheriff's office identified the assailant in a tweet as 26-year-old Snochia Moseley from Baltimore County.
The sheriff said investigators have not yet determined a motive, but a law enforcement source told Reuters the shooting was believed to have been sparked by a work-related grievance.
The fact that the assailant was a woman was unusual, given that the overwhelming majority of mass shootings in the United States are committed by men.
Gahler said Thursday's gun violence began outside the warehouse and then moved inside, but investigators were still piecing together the precise sequence of events.
He said a total of seven people were hit by gunfire and that four, including the woman who opened fire, were killed. The three others were expected to survive, according to the sheriff.
No shots were fired by any law enforcement officers, he said.
The Rite Aid centre, located among other warehouses in an industrial park, has nearly 1000 employees, company spokesman Pete Strella said. The facility packages pharmaceuticals and other products for delivery to more than 2500 stores.
Police spent several hours searching the building for any possible additional victims, the sheriff's office said.
"Our prayers are with all those impacted, including our first responders," Governor Larry Hogan wrote on Twitter. "The State stands ready to offer any support."
Agents from the Baltimore offices of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives and the FBI also responded, the agencies said.
The shooting occurred a day after a man shot and wounded four people, including a police officer, at a Pennsylvania court building before he was killed by police, according to Pennsylvania State Police.
