Whatever their rationale -- be it to help a friend or cover up for him -- the three men left with the backpack. Kadyrbayev said he took Tsarnaev's laptop computer too, because he felt Tsarnaev's roommate might get suspicious if they left with the backpack alone, the affidavit states.
They all ended up at Kadyrbayev's and Tazhayakov's New Bedford apartment. There they saw the news coverage on the bombings, wallpapered with photos of the two suspects.
Kadyrbayev and Tazhayakov "started to freak out, because it became clear from a CNN report that we were watching that (Dzhokhar Tsarnaev) was one of the Boston Marathon bombers," Phillipos told investigators.
The Cambridge resident said he didn't understand much of what Kadyrbayev and Tazhayakov said afterward because they talked mostly in Russian.
At some point though -- Kadyrbayev said it was later that night, Tazhayakov thought it was early the following morning -- Tsarnaev's backpack was put in a black garbage bag, lugged outside, and thrown in a dumpster.
This came after all three friends talked about what to do first, according to the affidavit. Phillipos' response, for instance, to Kadyrbayev: "Do what you have to do."
A garbage truck emptied that dumpster that Friday -- the same day that Tsarnaev was finally captured, hurting from apparent gunshot wounds to his head, neck and legs and hand, in the back of a boat parked in a Watertown, Massachusetts, backyard.
His friends weren't far behind in following him into federal custody.
After 10 hours of questioning that Friday, Kadyrbayev and Tazhayakov were detained the next day on alleged visa violations, according to Stahl.
Six days later, the backpack they'd thrown away was found -- this time in a New Bedford landfil. Inside was an assortment of fireworks, a jar of Vaseline and a homework assignment sheet from the University of Massachusetts-Dartmouth, among other items.
And on Wednesday, Kadyrbayev, Tazhayakov and Phillipos were in court accused of covering up for their friend, and hampering an investigation into the bloody attacks that jarred a city and a nation.