Dzhokhar Tsarnaev in serious condition, bled for hours before capture

The lone surviving suspect of the Boston Marathon bombing might not have lived through the night if police had not found him, according to new details released after the arrest.

Dzhokhar Tsarnaev was taken to a local Boston hospital in serious condition after police found him hiding in a boat in a backyard in suburban Watertown, Mass.

When he was taken into custody, the suspect was bleeding badly and too weak to resist any longer, officials said.

The homeowner who first saw Tsarnaev hiding in the boat told police he saw a lot of blood. 

According to CBS News senior correspondent John Miller, it's likely Tsarnaev was shot as long as 20 hours before being discovered.

His injury was probably sustained Thursday when Tsarnaev and his brother Tamerlan, who died that night, engaged fire in a "fierce gun battle with police," Miller said.

Police said later that Dzhokhar Tsarnaev had been shot in the neck and in the leg, according to CBS.

Miller said that images of a SWAT team medic administering an "ambu" resuscitation bag to assist Tsarnaev's breathing show that "this is a guy who was very weak at this point and probably — had he not been discovered — he might not have lived."

Investigators are hoping that the younger Tsarnaev survives so they can discover what might have motivated the 19-year-old and his brother to allegedly launch the attacks that killed three, including a young boy, and wounded more than 170.

The brothers are also accused by investigators of shooting and killing MIT security officer Sean Collier and badly wounding a Boston transit cop on Thursday night.

The hospital treating Tsarnaev has not released any updates.

Correction: This story has been updated from a previous version. MIT security officer Sean Collier was killed and a transit officer wounded on Thursday night, not Wednesday. The language of this article has been adjusted to clarify that the brothers are suspects, and have not been proven responsible for any crimes.