Shots were reportedly fired in the Emmorton Business Park before 9:30 a.m. Wednesday.
Multiple deaths and injuries have been reported and businesses in the area are on lockdown. Some schools have also been placed in modified lockdown status.
The shooting is described as workplace violence at a granite company in the Emmorton Business Park.
The suspect in is identified as 37-year-old Radee Prince. Police say he may be driving in a black GMC Acadia (Delaware plates PC064273) and advise anyone who sees him to call 911.