Boston Bombings 2013: 'Chilling' unreleased video clearly shows youngest Boston bomber placing backpack on floor Surveillance video from the Boston Marathon attack shows one suspect dropping his backpack and calmly walking away from it before the bomb inside it exploded, Massachusetts Governor Deval Patrick said Sunday. The video clearly puts 19-year-old Dzhokhar Tsarnaev at the scene of the attack, Patrick said on NBC. It does seem to be pretty clear that this suspect took the backpack off, put it down, did not react when the first explosion went off and then moved away from the backpack in time for the second explosion," Patrick said. A new report claims that Dzhokhar Tsarnaev (left) is seen in unreleased video to calmly place an explosive device on the ground at the Boston marathon and walk away seconds before it detonates 'It's pretty clear about his involvement and pretty chilling, frankly.' He added, however, that he hasn't viewed all the tapes but had been briefed by law enforcement about them. Investigators have determined the bombs were fashioned from pressure cookers packed with explosives, nails and ball bearings and hidden in black backpacks. Three people were killed and more than 180 injured when the two bombs exploded Monday about four hours into the race. Dzhokhar Tsarnaev (circled in red) is seen making his way from the scene of the second detonation on Monday at the Boston marathon Tsarnaev was captured Friday after being pulled bloody and wounded from a tarp-covered boat in a suburban Boston backyard. He is being guarded by armed officers while he recovers at a Boston hospital. He is in serious condition and hasn't been able to communicate with investigators. His 26-year-old brother and alleged accomplice, Tamerlan, died earlier Friday after a gunbattle with police. The brothers are also suspected of killing an MIT police officer Thursday and severely injuring a transit officer. Patrick said Sunday on CBS' 'Face the Nation' that law enforcement officials believe the immediate threat ended when police killed Tamerlan Tsarnaev and captured Dzhokhar. This frame grab from a video released by the FBI on Thursday, shows Tamerlan Tsarnaev (left) in black cap, walking ahead of his brother Dzhokhar Tsarnaev (right in white cap) around 15 minutes before they detonated their bombs at the Boston marathon The moment the second Boston bomb detonated can be clearly seen as the smoke cloud from the first blast billows in the distance Horror: The scene after explosions at the Marathon finish line in Boston, Massachusetts - Three people were killed and over 180 were injured when two bombs exploded on 15 April 2013 The governor said he has no idea why someone would deliberately harm 'innocent men, women and children in the way that these two fellows did.' On Saturday, Patrick appeared on the field at Fenway Park with dozens of local and state police before the Boston Red Sox's first home game since the bombings. Meanwhile, Boston Mayor Thomas Menino told ABC's 'This Week' that he hopes authorities "throw the book" at Dzhokhar Tsarnaev. 'I hope that the U.S. attorney takes him on the federal side and throws the book at him,' Menino said. These two individuals held this city hostage for five whole days. 'They should not do that -- that's what these terrorist events want to do, hold the city hostage and stop the economy of the city.' Krystle Campbell. Campbell, 29, a restaurant manager from Medford, died in the blasts as did eight-year-old Martin Richard (right) Lu Lingzhi, the 23-year-old Boston University graduate student was named the day after the explosions as the third victims of the Tsarnaev brother's terror attacks Menino also said information he has indicates that the suspects in the Boston Marathon bombing acted alone. Menino tells 'This Week' that he agreed with the decision to lock down Boston all day Friday, based on information officials had at the time. He tells 'This Week' that a pipe bomb was found at another location and that another person was taken into custody. The mayor did not elaborate. A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene in a wheelchair