U.S. Capitol Police Chief Matthew Verderosa said one bystander was injured, though apparently not severely, in the incident.

Speaking to reporters, Verderosa also corrected initial reports that a U.S. Capitol Police officer had been shot. The police chief said "no officers were injured."

"There is no reason to believe that this is anything more than a criminal act," he said.

The chief's brief comments helped bring some measure of clarity to the confusion on Capitol Hill, two hours after reports first surfaced of shots being fired – all occurring a week after the Brussels terror attack put major cities around the world on high alert.

The chief said the suspect was transported to the hospital and is undergoing surgery. "His condition is unknown at this time," he said.

Fox News is told the suspect has been identified as Larry Dawson. Officials said he is known to law enforcement, and Verderosa said he's frequented the Capitol grounds before.