A woman Thursday shot three people dead and injured three more at a warehouse complex in Maryland, according to police.
The incident in Aberdeen, around 48 km from Baltimore, ended when the shooter, 26, turned the handgun on herself, they added. She later died in hospital.
The three injured people were expected to survive, Sheriff Gahler from Harford County said in a press conference.
The shooter, a temporary employee who reported for work as usual, began firing outside the pharmacy distribution centre just after 9 am local time, then inside the facility, with a 9mm Glock handgun, Harford County Sheriff's Office said.
The motive for her attack was unclear.
The police and agents from the FBI and a customs agency all responded but no shots were fired.
The sheriff's office initially told residents to avoid the area, later saying it did "not believe there is any further threat to the community".
Governor of Maryland Larry Hogan called the shooting "tragic" and thanked first responders for their actions.