A 26-year-old woman opened fire at a Rite Aid distribution center in Aberdeen, Md., on Thursday morning, the authorities said, killing three people and wounding several others in what was the nation’s third shooting at a workplace in less than 24 hours.

The assailant, Snochia Moseley, a temporary employee at the facility, shot herself and died at a hospital, Sheriff Jeffrey R. Gahler of Harford County, Md., said at a news briefing. Ms. Moseley, whose last known address was in Baltimore County, had reported for work as usual before carrying out the attack with a single weapon, a Glock 9-millimeter handgun.

“We believe the shooting incident began outside and then moved into the front of the building,” Sheriff Gahler said, adding that the investigation was still preliminary.

Two of the victims died at the scene, while another died at a hospital, he said. Three people were wounded and are expected to survive. Sheriff Gahler did not identify the victims.