New photos, taken with thermal imaging cameras, reveal how breakthrough technology helped police home in on the second Boston Marathon bombing suspect 19-year-old Dzhokhar Tsarnaev.

The pictures reveal how state-of-the-art thermal imaging cameras helped police track the Chechen terror suspect while he hid on David Henneberry’s boat for his final stand off in Watertown following a terrifying week of violence.

David Henneberry called 911 after spotting blood and what he thought was a crumpled body in his boat, which was sitting in the backyard of his home.

Authorities then used a helicopter equipped with a thermal imaging device to confirm that there was a body in the tarp covered boat and that the person was alive.

Hovering over the area, the helicopter spotted the heat signature of a person, confirming David Henneberry’s suspicions.

“Our helicopter had actually detected the subject in the boat,” Col. Timothy Alben of the Massachusetts State Police told NBC News.

“We have what’s called a FLIR – a forward-looking infrared device – on that helicopter.”

State-of-the-art thermal imaging cameras helped police track Dzhokhar Tsarnaev while he hid on David Henneberry’s boat in Watertown

The helicopter monitored the body in the boat for more than an hour before police moved in and took the bleeding Dzhokhar Tsarnaev into custody.

Dzhokhar Tsarnaev remained in hospital today and was described as clinging to life as Massachusetts Gov. Deval Patrick said: “I hope he survives, because we have a million questions.”

The secret service’s top interrogators are now waiting to quiz Dzhokhar Tsarnaev as he is treated in the same hospital where 11 victims are still recovering.

Thermal imagers are able to detect a body or other heat source inside a house, a vehicle, or in this case, a boat, because heat, unlike visible-light wavelengths can pass through walls.

Police regularly use them to find out whether marijuana is being grown inside a house with heat lamps.

David Henneberry became the day’s unusual hero when he decided to check on his beloved boat moments after police lifted a Boston-wide lock-down believing they wouldn’t find Dzhokhar Tsarnaev.

Unconfirmed reports suggest that Dzhokhar Tsarnaev was shot twice by law enforcement in the gun battle which raged until his capture at approximately 8.45 p.m.

Law enforcement sources have suggested that Dzhokhar Tsarnaev gave himself up voluntarily after realizing continuing resistance was fruitless.

President Barack Obama praised the outcome after a “tough week” but said the focus would now be on getting answers for the victims.

He said: “Why did young men who grew up and studied here as part of our communities and our country resort to such violence?”

“We’ve closed an important chapter in this tragedy,” added Barack Obama said in his televised address.

Meanwhile, federal law enforcement officials are invoking the public safety exception to the Miranda rights.

That means that Dzhokhar Tsarnaev will be questioned immediately without having his rights read to him.

Republican Senators John McCain and Lindsey Graham have called for Dzhokhar Tsarnaev to be held as an enemy combatant, although the chances of that being permitted are slim.

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