(WASHINGTON) -- Several governmental buildings in Washington, D.C., were evacuated Thursday morning due to what Capitol Police called "an active bomb threat investigation" after a man drove a pickup truck onto a sidewalk.
The bomb-threat suspect, 49-year-old Floyd Ray Roseberry of North Carolina, surrendered Thursday afternoon and is in custody, said Capitol Police Chief J. Thomas Manger.
It's still unclear whether there were explosives in his truck, Manger said in an afternoon news conference.
Roseberry had been sitting in his truck for several hours in front of the Library of Congress and said he had explosives, Manger added. Responding officers said he had what appeared to be a detonator in his hand.
Authorities tried to negotiate with Roseberry by writing messages on a whiteboard, Manger said. Authorities then used a robot to give the suspect a phone, but he wouldn't use it.
Roseberry then exited his truck and surrendered without incident. It's unknown what his motive may have been, and authorities said they've contacted his family.
He doesn't have a serious criminal background, police added.
Authorities are also investigating a video posted to Facebook that appears to have been posted by the suspect.
The Cannon House Office Building, a congressional office building, was evacuated via underground routes. The Library of Congress and Supreme Court building also were evacuated. Both the Supreme Court and Congress are on recess.
Messages were sent to congressional staffers asking that they "remain calm and relocate to Longworth House Office Building using the underground tunnels."
Senate staff were asked in a message to "remain clear of the police activity" and to "please move indoors" if they were outside on Capitol grounds.
The White House said it was monitoring the situation and was receiving updates from law enforcement, according to an administration official.
D.C.'s Metropolitan Police Department said later Thursday afternoon that the truck was cleared and road closures were lifted.
"Residents may return to their homes," police tweeted. "Thank you all for your patience during this critical incident."
House Speaker Nancy Pelosi said in a statement, "Today, once again, the Capitol Police, FBI and other law enforcement dealt with a potential threat to the Capitol Hill community. The immense gratitude of the Congress is with all law enforcement officers who today and all days sacrifice to keep the Capitol Complex and those within it safe."
This is a developing story. Please check back for updates.