WASHINGTON (CNN) -- Police arrested a man near the U.S. Capitol on Tuesday after he drove up to one of the building's barricades with a rifle in his vehicle and told officers that he had a delivery for President Obama, a Senate spokesman said.

A man drove to the Capitol with a rifle and said he had a delivery for President Obama, police said.

Sgt. Kimberly Schneider identified the man as Alfred Brock, 64, of Winnfield, Louisiana. She said Brock was charged with possession of an unregistered firearm and unregistered ammunition.

Brock drove up to the north barricade at the Capitol late Tuesday afternoon, saying he had a delivery for the president, Schneider said.

After further questioning, he admitted he had a rifle in his truck. He was arrested and taken to police headquarters for processing, she said.

A search of his truck turned up several rounds of ammunition, Schneider said. Police also checked the area around the barricade, but found nothing hazardous.

Threats against Obama have led to arrests in previous cases.

In one, federal prosecutors concluded that three people arrested with drugs and weapons in a suburban Denver, Colorado, motel posed a "true threat" to Obama during the Democratic National Convention.

In the second, a Florida man was charged with threatening bodily harm against the then-candidate in August. He has pleaded not guilty.

All About Barack Obama • U.S. Capitol