Officials: Dzhokhar Tsarnaev Was Not Armed When Apprehended

BOSTON (CBS) - At the final take down at the Watertown boat, officials confirm Dzhokhar Tsarnaev was not armed.

There was gunfire from police when they approached and saw movement in the boat.

WBZ-TV has learned that an MBTA Police Sgt. Michael Adamson was hit with a ricocheted bullet that night. He was injured in the hip and treated at the scene.

This followed a firefight earlier in the night.

Officials confirm earlier in the night, the brothers were armed with a metal pressure cooker handmade grenades but just one gun.

One law enforcement official said the gun's serial number "hand been obliterated" making it difficult to trace.

Investigators say it was probably stolen or purchased on the street.

Investigators believe the brothers used a remote control detonator to ignite the bombs at the finish line.

The entire plot - they believe - financed through drug sales.

Sources tell CBS News that Tamerlan Tsarnaev who was unemployed, made money selling marijuana.

The FBI knows Tamerlan spent $200 in February buying mortar shells and they think the brothers used black powder from those fireworks shells as the explosive in the pressure cooker bombs.

Agents are also visiting gun shops in the area to determine if the brothers bought other ammunition or gunpowder.

There is still no evidence that the brothers had outside help or worked with a terror group.

Boston Police Commissioner Ed Davis said that is troubling.

"Our fear of a lone wolf who is getting instruction from Inspire Magazine and going out and doing things they advocate is very difficult to intercept," Davis said.