There is word that the Boston Marathon bombing suspect, Dzhokhar Tsarnaev is awake and responding to questions, in writing.  ABC News reports investigators are asking about other cell members and other unexploded bombs.

Tsarnaev, 19, is being treated at Beth Israel Deaconess Medical Center in Boston, where he is listed in serious but stable condition, with wounds to the neck and throat area, according to sources.

The bombing killed three, including a young boy, and wounded about 170. An MIT officer was allegedly killed by Tsarnaev and his brother  26 year old Tamerlan Tsarnaev and a Boston transit cop was badly wounded in a subsequent shootout.

He apparently knows that his brother died after a Thursday night gun battle with police, sources say.

Police believe Tsarnaev was initially wounded Thursday night in the gun battle that ended in his brother's death. Police said they found blood in a car he abandoned and blood at a house.

Friday authorities launched  a manhunt for Tsarnaev, who managed to escape one block outside a police perimeter.  Authorities zeroed in on a boat in a Watertown, Mass., backyard after they received a tip from a homeowner.

An infrared camera with a bird's-eye view of the moments before Tsarnaev's capture gave authorities an idea of what to expect as they methodically closed in on the Boston Marathon bombings suspect.

The thermal-imaging camera showed Tsarnaev was able to move around inside the boat, as the FBI SWAT team brought in a robotic device to approach the boat and peel back a tarp, giving authorities a clear view of the suspect.

At least two flash grenades were thrown into the boat, designed to disorient Tsarnaev, who authorities feared might have been wearing a suicide vest.

They were then able to move in, rushing Tsarnaev to Beth Israel medical center for treatment, where he has remained under heavy guard. He was not wearing a vest.

Tsarnaev is in the same hospital where his brother, Tamerlan, 26, was brought early Friday after a shootout with police. Tamerlan died of his wounds.