A police chopper equipped with a thermal imager picked up on Boston Marathon bombing suspect Dzhokhar Tsarnaev's body heat through a tarp in a Watertown, Mass. resident's boat, helping in the arrest.
Massachusetts State Police The suspect was hiding inside a 1980s pleasure boat owned by Watertown, Mass. Resident David Henneberry.
There was no way out for Dzhokhar Tsarnaev.
The Boston bombing suspect was crammed on the floor of a boat as law enforcement closed in during Friday's massive manhunt, according to newly released aerial video.
A helicopter, using thermal imaging, caught the action as the arm of an armored tank peeled back tarp that covered the 24-foot boat — which was parked behind a residential home in Watertown, Mass.
Massachusetts State Police Dzhokhar Tsarnaev’s feet can be seen at the center of this image captured by an infrared device.
Then, small explosives — believed to be flash-bang grenades — were tossed into the front of the boat in an attempt to stun Tsarnaev. Such devices are non-lethal.
Earlier still images released by Massachusetts State Police were of those same dramatic moments before Tsarnaev was captured. The new video doesn't include sound.
"We have what's called a FLIR — a forward-looking infrared device — on that helicopter. It picked up the heat signature of the individual," said Col. Timothy Alben of the Massachusetts State Police.
Massachusetts State Police When the boat's owner lifted up the tarp covering his boat, he saw a pool of blood and what he thought looked like a body, according to reports.
Police had the helicopter fly over the man's house after he reported that a bloodied person was holed up in his boat, which was just outside the search perimeter police set up earlier in the day.
Although obstructions — such as the boat tarp — can prevent light from passing through, heat waves can still be detectable, said NBC News.
Authorities saw what is called an infrared signature — the way an object or person appears beneath thermal sensors. Infrared signatures can help monitor volcanoes or detect diseases, but it also helped police monitor Tsarnaev's body for more than an hour.
Massachusetts State Police
Cops used a forward-looking infrared device (FLIR) to find traces of Tsarnaev’s heat signature.
Massachusetts State Police
After the boat's owner reported his suspicions, cops descended on the scene and captured the suspect.
An FBI officer stands in front of the boat at 67 Franklin St. in Watertown, Mass. where Dzhokhar Tsarnaev, the surviving suspect in the Boston Marathon bombings, was found hiding Friday night.
