Her name was not immediately released.
Harford sheriffs also reported that Moseley was a temporary employee of the facility and showed up for "her work day as usual around 9 am".
Witness Colleen Hendrickson said: "I think it's real for a lot of people right now, and there's a lot of people still affected by this, [police] are still looking, and it's been a few hours at this point, or about an hour and a half".
She was already down when officers arrived and an officer moved her from the scene, not knowing that she was the shooter, he said.
"She didn't have a particular target".
He says she pulled a hooded shirt over her head and began shooting, striking and killing Aguda outside the building.
Area hospitals reported receiving five patients from the incident.
Before her death was announced, Dr Raymond Fang from Johns Hopkins Bayview Trauma Center facility was treating four people for gunshot wounds.
The woman, whom Mr Gahler declined to identify, had "two, perhaps three" extra clips of ammunition.
Tightening Texas race boosts Democrats’ hopes of taking U.S. Senate
Quinnipiac previously polled registered voters three times, finding Cruz ahead by 6 points in August, 11 in May and 3 in April. The poll also showed Florida's Republican governor, Rick Scott, with a 1-percentage-point lead over Democratic U.S.
Three other wounded people were being treated at a hospital.
A law enforcement official later confirmed to the Associated Press that a number of people had died in the incident.
The woman who shot and killed three people at a warehouse in the USA state of Maryland had been employed at the business for less than two weeks.
"We do not have a motive for this senseless crime", he said, but terrorism did not appear likely. "It's so important that we deal in facts".
Federal Bureau of Investigation tactical agents prepare as police search for a gunman who fled the scene of a shooting at a Rite Aid Distribution Center in Aberdeen, Maryland, USA, Sept. 20, 2018.
Carre locked the doors of his workplace after the injured man came hobbling in, bleeding from his leg.