The changing facts in the Boston investigation Important details like the suspects' weapons, NYC plans and the shootout keep changing. It's fueling conspiracies

In the aftermath of massive, complicated crimes it's not uncommon for a bit of crucial information to be immediately put forward by police, only to be contradicted later on. While it's understandable that initial leads and assertions might end up being wrong in a dynamic situation like the aftermath of the Boston Marathon bombing, wholesale contradictions can encourage skepticism of the motives of those releasing inaccuracies -- as with initial, false reports that Osama bin Laden hid behind his wife when U.S. forces shot him. Another effect of changing details can be to encourage conspiracy theorists who latch onto inconsistencies, and to undermine trust in authorities.

Now, almost a week after the Tsarnaev brothers fought a rolling street battle with dozens of heavily armed police officers, we learned Wednesday night that they had only a single handgun, according to sources who spoke with ABC News and the AP, something that directly contradicts what officials had previously said.

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Here are some of the biggest changes to facts released in this investigation:

Suspects' arms - After the manhunt, Boston Police Commissioner Ed Davis said the brothers were "heavily armed" and numerous reports detailed a fairly extensive arsenal. According to a New York Times report from April 21 citing a law enforcement official, "The authorities found an M-4 carbine rifle ... two handguns and a BB gun." Now unnamed sources say there was only a single 9mm pistol between the two brothers. Indeed, photos of the shootout suggest only one brother had a weapon.

- After the manhunt, Boston Police Commissioner Ed Davis said the brothers were "heavily armed" and numerous reports detailed a fairly extensive arsenal. According to a New York Times report from April 21 citing a law enforcement official, "The authorities found an M-4 carbine rifle ... two handguns and a BB gun." Now unnamed sources say there was only a single 9mm pistol between the two brothers. Indeed, photos of the shootout suggest only one brother had a weapon. Boat gunfight? - Police initially reported that Dzhokhar Tsarnaev fired on police when they found him hiding in a boat Friday night. “It was back and forth ... yes — he was firing," Watertown Police Chief Ed Deveau told CNN Saturday (though the FBI cautioned at the time that only federal authorities had official information). In its definitive "tick tock" of the events, the Washington Post reported that the suspect inside the boat "was shooting back." But later, the Washington Post and the AP reported yesterday that Tsarnaev was unarmed when police found him after what what was described as a gunfight. As it turns out, police may have been spooked by an errant shot, and fired into the boat, but apparently zero shots came out.

- Police initially reported that Dzhokhar Tsarnaev fired on police when they found him hiding in a boat Friday night. “It was back and forth ... yes — he was firing," Watertown Police Chief Ed Deveau told CNN Saturday (though the FBI cautioned at the time that only federal authorities had official information). In its definitive "tick tock" of the events, the Washington Post reported that the suspect inside the boat "was shooting back." But later, the Washington Post and the AP reported yesterday that Tsarnaev was unarmed when police found him after what what was described as a gunfight. As it turns out, police may have been spooked by an errant shot, and fired into the boat, but apparently zero shots came out. 7 -Eleven and the MIT officer - Initial reports suggested the brothers tried to hold up a 7-Eleven, and then killed an MIT officer who either responded to the robbery or just happened to be in the area. But days later, authorities revealed that the holdup was committed by different suspects and the confusion was caused by the close proximity of the two events. It's still unknown exactly why the brothers killed the police officer.

- Initial reports suggested the brothers tried to hold up a 7-Eleven, and then killed an MIT officer who either responded to the robbery or just happened to be in the area. But days later, authorities revealed that the holdup was committed by different suspects and the confusion was caused by the close proximity of the two events. It's still unknown exactly why the brothers killed the police officer. Carjacking - Some reports indicate that the person whom the brothers carjacked escaped while they inexplicably went into a store to buy snacks, while others say the brothers let the victim go because he wasn't American. It's also still unclear which brother stole the black SUV, and which drove the Honda that followed.

- Some reports indicate that the person whom the brothers carjacked escaped while they inexplicably went into a store to buy snacks, while others say the brothers let the victim go because he wasn't American. It's also still unclear which brother stole the black SUV, and which drove the Honda that followed. Trip to NYC - What the suspects did after the bombing remains a mystery, but one detail that emerged was that they were planning to head to New York City -- to party. That's what New York Police Commissioner Ray Kelly said yesterday. But today, NBC News reports the brothers discussed trying to detonate a bomb in Times Square, but that the plan was not well developed and “aspirational at most.”

What the suspects did after the bombing remains a mystery, but one detail that emerged was that they were planning to head to New York City -- to party. That's what New York Police Commissioner Ray Kelly said yesterday. But today, NBC News reports the brothers discussed trying to detonate a bomb in Times Square, but that the plan was not well developed and “aspirational at most.” Perimeter - As the New York Times reported Wednesday, "Police officials initially said the boat was in the backyard of a house just outside the perimeter of the area where investigators had conducted door-to-door searches all day. But Commissioner Davis, of the Boston police, said this week that the boat had been inside the perimeter."

We'll update this post as more examples emerge.