Shortly before midnight, Officer Tia Bynum, 28, of Catonsville, was traveling westbound on Route 40 with her patrol vehicle's lights and sirens activated, responding to a call for assistance from another officer, said Louise Rogers-Feher, a police spokeswoman.
As Bynum, a six-year veteran of the force, began entering the intersection of Route 40 and Coleridge Road against a red traffic light, another vehicle heading south on Coleridge which had a green light entered the intersection, Rogers-Feher said.
To avoid a collision, Bynum swerved, Rogers-Feher said.
"She was doing everything right. She had her siren on, she had her lights on, so people were given notice that the vehicle was moving" through the intersection, Rogers-Feher said. "She also didn't want to hurt anyone, so she swerved."
Doing so caused Bynum to lose control of her 2010 Ford Crown Victoria, which began spinning, Rogers-Feher said.
The wheels and undercarriage of Bynum's patrol car struck the north-side curb of Route 40 before continuing into a tree, which struck the driver's door of the patrol car, Rogers-Feher said.
The driver of the other vehicle that had entered the intersection, who has not been identified, was not involved in the collision and did not stop, Rogers-Feher said.
When emergency responders arrived at the scene shortly after, they found Bynum's patrol car badly damaged, so much so that Bynum had to be cut free from the vehicle, a fire dispatcher said.
Rogers-Feher said she could not describe the exact injuries Bynum sustained, but said at the time she was extricated from the vehicle, they were "considered severe."
Bynum was transported to Maryland Shock Trauma Center, in part so doctors could "make sure she had no internal problems," Rogers-Feher said.
However, that did not appear to be the case, as Bynum was discharged from the hospital at 5:30 a.m. Thursday, Rogers-Feher said.
"Apparently, the angels were on her shoulder," she said.