An alchemy of police work, citizen involvement and technology yielded crucial big breaks in the Boston Marathon terror attack case and brought the manhunt to a quick conclusion, experts say.
Good citizenship came from a carjack victim and a boat owner, whose calls put police directly on the suspects' trail.
Technology yielded the first major break when police found photos and even a surveillance video of the two suspects, Tamerlan Tsarnaev, 26, and his brother, Dzhokar Tsarnaev, 19, toting backpacks at the marathon's home stretch.
"Cameras seemed a useful technology in finding these people and solving this quickly," CNN quoted Neil Richards, a law professor at Washington University School of Law in St. Louis, as saying.
The next big break came during the pre-dawn hours of Friday when a motorist was carjacked and taken hostage.
The two carjackers told the driver that they bombed the Boston Marathon and just killed a police officer.
The brothers then acquired another vehicle in a manner that authorities have yet to detail, the report said.
But it was the first vehicle, a carjacked Mercedes SUV, that gave police a stroke of technological fortune.
The carjacking victim left his cell phone in the SUV.
"Lucky for him and lucky for us that his cell phone remained in that vehicle," said Police Chief Edward Deveau of Watertown, Massachusetts.
Police began tracking the cell phone and the Tsarnaev brothers themselves. They were in Watertown, a suburb of Boston, where police engaged them, now in two cars, in a fierce gunfight. One of them also threw bombs at police.
But as police handcuffed the older brother, the younger barreled toward them in the carjacked SUV. He then drove over his older brother, dragging him a short distance down the street, police said.
Authorities did not have an immediate explanation as to why he ran over his big brother.
The younger brother - now the only surviving suspect - ditched the car and escaped into the dark streets.
As media outlets reported the dramatic shootout the next morning, the manhunt reached its highest intensity.
A homeowner who noticed something amiss late Friday with a tarp covering his boat, stowed in his backyard since winter. A peek inside by owner David Henneberry revealed a pool of blood and a silhouette in the darkness of someone, curled up.
Henneberry's call to 911 brought about 2,000 law officers and their technology to the scene.
In the night air, a police helicopter used infrared cameras to see Tsarnaev's movements inside the boat.
"The technology is called 'flir,' forward looking infrared," said former FBI assistant director Tom Fuentes. "The human body is warmer than the air around him, so it stands out," Fuentes said.
Bloodied and injured, he surrendered, his capture made possible by police, thermal-imaging technology and a citizen's wisdom to run to the phone.
