The man banged on the glass doors of WMAR-TV in Towson, asking to be let inside. When he was refused, he crashed a large commercial truck into the ABC affiliate's lobby at 11:45 a.m., station employees told CBS television.
A spokeswoman with the Baltimore County Police Department said officers evacuated 55 people from the building and urged others to avoid the area.
Police said they were looking for the suspect inside the building after officers did not find him in the vehicle, which remained in the lobby of the station.
"We don't know who he is, and we certainly don't have any info as to what his motive is," police spokeswoman Elise Armacost told a news conference.
Armacost said there were no reports of injuries but that additional people may still be sheltered in place. She said the suspect may be armed but there were no reports of shots fired.
Brian Kuebler, a reporter at the station, said on Twitter the suspect rammed the building three times with a landscaping truck.
He "tried to get in (the) building screaming 'LET ME IN!' and said he was God," according to Kuebler's Twitter post.