UPDATE 9-Shooting at Rite Aid warehouse in Maryland leaves 4 dead, including suspect

A woman armed with a handgun opened fire on Thursday at a Maryland distribution center for the Rite Aid drugstore chain, killing three people and wounding three others before she took her own life, the Harford County sheriff said.

A woman armed with a handgun opened fire on Thursday at a Maryland distribution center for the Rite Aid drugstore chain, killing three people and wounding three others before she took her own life, the Harford County sheriff said.

The shooting unfolded shortly after the suspect, a temporary employee at the facility, reported for work at about 9 a.m. EDT (1300 GMT) at the warehouse in Perryman, Maryland, about 34 miles (55 km) northeast of Baltimore, Sheriff Jeffrey Gahler said at a news conference.

The sheriff's office identified the assailant only as a 26-year-old woman whose last known address was in 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 marked an unusual circumstance in and of itself as the overwhelming majority of mass shootings in the United States are committed by men.

Gahler said the shooting began outside the warehouse and then moved inside. He said a total of seven people were hit by gunfire and that four, including the woman who opened fire, were killed. He said the suspect shot herself in the head.