Physical evidence recovered from the site of the shootout between police and the Tsarnaev brothers and in a vehicle they are suspected of carjacking has been linked to the explosives used in the Boston Marathon bombings, according to an FBI affidavit released Monday.
The explosives recovered from the three sites had "similarities," the affidavit said, and a pressure cooker found at the scene of the Watertown shootout was the same brand used in the marathon bombings, according to the affidavit by Special Agent Daniel R. Genck of the FBI's Boston field office.
The affidavit also provided a timeline of the movement of brothers Tamerlan and Dzhokhar Tsarnaev as they allegedly approached the marathon finish line a week ago Monday to plant two explosives that killed three people and injured more than 170.
The affidavit was presented to support charges against the surviving brother, Dzhokhar, 19, who is identified as "Bomber Two." Tamerlan Dzhokhar, 26, killed in the Watertown shootout, was referred to as "Bomber One."
Dzhokhar Tsarnaev could face the death penalty in the April 15 bombings at the Boston Marathon, prosecutors announced Monday.
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Tsarnaev was charged with conspiring to use a weapon of mass destruction "against persons and property in the U.S. resulting in death" and one count of malicious destruction of property by means of an explosive device resulting in death, according to the U.S. attorney's office in Massachusetts.
The affidavit says that at 2:38 p.m. that day "two young men can be seen turning left (eastward) onto Boylston [Street] from Gloucester Street. Both men are carrying large knapsacks."
Three minutes later, the two men can be seen standing about a half-block from the Forum Restaurant, video from the restaurant's security cameras show, the affidavit said.
One minute later, at 2:42 p.m., one of the men, later identified as Tamerlan, heads east on Boylston Street toward the finish line. The man later identified as Dzhokhar followed, the affidavit said, and stopped in front of the restaurant and apparently slipped his knapsack onto the ground, according to the affidavit.
About 30 seconds before the first explosion, Dzhokhar appears to be speaking on his cellphone for about 18 seconds, the affidavit said. The first explosion came seconds later, and "Virtually every head turns to the east (toward the finish line) and stares in that direction in apparent bewilderment and alarm," the document said.
"Bomber Two, virtually alone among the individuals in front of the restaurant, appears calm," the affidavit said. "He glances to the east and then calmly but rapidly begins moving to the west, away from the direction of the finish line.
"He walks away without his knapsack, having left it on the ground where he had been standing," the document said. "Approximately 10 seconds later, an explosion occurs in the location where Bomber Two had placed his knapsack."
In addition to the physical evidence, the affidavit said, the agent compared the images from the surveillance cameras with the brothers' records from the Massachusetts Registry of Motor Vehicles and concluded that they were the same people.