The shooting occurred shortly after 9 a.m. EDT (1300 GMT) in Aberdeen, about 34 miles (55 km) northeast of Baltimore.
“I can confirm multiple wounded and multiple fatalities,” Harford County Sheriff Jeffrey Gahler told reporters at a news briefing. He did not offer any details regarding the suspect’s identity or a possible motive behind the shooting.
An NBC reporter, Pete Williams, said multiple law enforcement sources told him the shooter was a woman.
A law enforcement source told Reuters that officials believe the suspect had a work-related grievance.
The Rite Aid center sits among a number of warehouses. The facility has nearly 1,000 employees, company spokesman Pete Strella said.
The shooting took place a few miles from the Aberdeen Proving Ground, a large Army facility where military technology is developed and tested, according to Harford County’s website. Agents from the Baltimore offices of the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) 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.