An 18-year-old ran towards the west front of the United States Capitol carrying a loaded shotgun, and additional rounds, before being apprehended by police, US Capitol police chief Michael Sullivan said today.

The incident started when a white Mercedes SUV parked in the 100 block of Maryland Avenue SW, Sullivan said at a news briefing.

A man wearing a tactical vest and tactical gloves got out of the vehicle with a shotgun and began running towards the Capitol.

According to Sullivan, Capitol police officers, with firearms drawn, ordered the man to drop the weapon as he reached the base of the west front steps and he “immediately complied”.

He then lay down on the ground and was taken into custody. There were no injuries reported.

In the vehicle, officers found a Kevlar helmet and a gas mask, according to Sullivan.

“We are unaware of a motive at this time,” he said. He asked anyone with cellphone footage of the incident to send it to Capitol police.

Carter Camacho faces charges including carrying a rifle without a licence and unregistered firearm and ammunition. File Photo / 123rf

Officials identified the man as Carter Camacho, of Smyrna, Georgia. He has been charged with unlawful activities, carrying a rifle without a licence, unregistered firearm and unregistered ammunition, Capitol police said in a statement.

The 18-year-old does not live in the area and has multiple addresses, Sullivan said. The vehicle, which was found in front of the US Botanic Garden, was not registered to him. Police did not say where the vehicle was registered.

The threat assessment section of the Capitol police is investigating the motive. Efforts to reach relatives of Camacho were unsuccessful.

A few months earlier, officers took part in an active-shooter exercise on the west front, close to where today’s incident unfolded, Sullivan said. He said officers do such exercises every month, and “that’s why we do it”.

Sullivan commended officers and said, “Who knows what could have happened if we would not have had officers standing guard like they do every single day”. Congress is not in session this week.

People trying to visit the US Botanic Garden were stopped by yellow caution tape cordoning off the area.

Capitol police officers began removing the tape this afternoon.