UPDATE: According to CNN, the suspect has been identified as a female "disgruntled" employee at Rite Aid.
The attack, which occurred at the drugstore distribution center, left three dead, with the alleged gun woman in critical condition after shooting herself twice in an unsuccessful suicide attempt.
Sheriff Jeffrey Gahler said at a news conference that the unnamed suspect used a single handgun, adding that no shots were fired by law enforcement.
The Baltimore Sun reported four people have been taken to the Johns Hopkins Bayview Medical Center for gunshot wounds.
Dr. Raymond Fang, Bayview trauma medical director told the publication that two patients were "very seriously injured" while the others were in stable condition.
He would not reveal if the shooter was one of the hospital's patients.
Just after 9 a.m. Thursday morning, gunshots were reported in Aberdeen, just northeast of Maryland.
The Hartford Country Sheriff's Office sent out a tweet in which they urged people to avoid "the area of Spesutia Road and Perryman Road," which is about 30 miles from Baltimore.
They revealed that there have been multiple victims and that the "situation is still fluid."
We can confirm there was a shooting in the area of Spesutia Road and Perryman Road. Multiple victims. The situation is still fluid. Please avoid the area. Media staging area still TBD.— Harford Sheriff (@Harford_Sheriff) September 20, 2018
Shortly after, the the FBI's Baltimore field office confirmed that an "active shooter situation" is currently underway in the aforementioned area and that special agents are "responding and assisting" the Sheriff's Office.
So far, it's unclear if the shooter targeted a specific business or if the incident took place outside.
Law enforcement officials have also refused to release any information regarding the nature of the injuries the victims sustained, or whether or not there are any fatalities in what is now described as a "horrific shooting."
No reports of an arrest have been made either.
"We are closely monitoring the horrific shooting in Aberdeen. Our prayers are with all those impacted, including our first responders. The State stands ready to offer any support," Maryland Gov. Larry Hogan said.
We will bring you updates as we receive more information about this terrible situation.
Our thoughts and prayers are with those affected by this act of violence.