This will make you wonder where Boston's brains went. It is a movie made by National Geographic. Below is a 2.39-minute trailer for the movie. Just go to 14 seconds. The narrator, Richard DesLauriers of the FBI, says "It was a video that showed a crowd watching the Marathon." The viewer may think we are looking at any grainy surveillance tape. But no, this is a re-enactment, filmed in Phoenix Arizona, starring Alec Karavey, as is announced in the Credits at the end.
At 31 seconds, FBI's Assistant Special Agent Jeffrey Sallett, says "There was just the slightest movement and you see the backpack, and you actually see the individual put it down."
No such thing happened in real life. There is no surveillance tape showing a guy put a backpack on the ground. Remember, this is a movie. Clever, eh? It was shown on TV before the trial and nearly every Bostonian would say "Yes, I saw it."
Note: There is an astonishing 2013 book by Trevor Aaronson, entitled "The Terror Factory," which tells how the FBI takes immigrants and inveigles them into a sting, giving them all the equipment needed for a bombing. But I do not draw any inference here, about Jahar Tsarnaev. He wasn't drawn into anything.
The first Jahar knew something funny was going on was when he heard his brother yell "Podstava." That's Russian for "I've been set up." This is the arrest of Tamerlan on Mt Auburn St. Start at 1.20 mins. It has been up for 7 years, made by Big Headphone (a video within Dee McLachlan's video):