Mayor Michael Bloomberg's organization Mayors Against Illegal Guns organized an event in Concord, New Hampshire, yesterday, during which the names of victims of gun violence since Newtown were read for several hours. Included among those names: Tamerlan Tsarnaev, the Boston bombing suspect killed during a shoot-out with police. But the group suggests it's not their fault. Tsarnaev's name came from a list posted at Slate.com, as Bloomberg's group told The Atlantic Wire on Wednesday afternoon.

The bizarre incident occurred during a stop on Mayors Against Illegal Guns' 25-state "No More Names" bus tour. The tour, meant to call attention to the number of people killed by guns over the six months since the shootings at Sandy Hook Elementary, stopped at the state capitol and several readers began listing the more than 6,000 victims.

Tim Buckland, a reporter from the New Hampshire Union Leader who was at the rally, mentioned the inclusion of Tsarnaev in a report about a scuffle between police and a protestor.

Some of the loudest shouts came when a reader spoke the name of Tamerlan Tsarnaev, one of the Boston Marathon bombing suspects who was killed by police during a gunfight.

"He's a terrorist," several protesters shouted.

That detail was spotted by the conservative commentator and MSNBC host S. E. Cupp, who tweeted about it. Mayors Against Illegal Guns, which has been outspoken in its efforts to get new legislation curtailing gun ownership passed, is a popular target of opposition among conservatives. So it was unsurprising when other conservative blogs quickly picked it up. (Update, 4:47 p.m.: A political opponent of Bloomberg's got in on the action, too.)

Rabbi Robin Nafshi of Temple Beth Jacob in Concord was at the event, and spoke with The Atlantic Wire by telephone this afternoon. She explained that she'd given an introductory prayer before the name-reading began — but left before any "controversial names" were read. It was her understanding, however, that the organizers of the event, who traveled to Concord on the bus, were the ones who put the list together.

Mayors Against Illegal Guns confirmed that much this afternoon — and also confirmed that Tsarnaev's name was read. In a statement provided to The Atlantic Wire, the group explained how that happened.

Mayors Against Illegal Guns relied on the public list compiled by Slate.com entitled 'How Many People Have Been Killed by Guns Since Newtown?', and his name was on the list. He was absolutely not a victim, his name should have been deleted before the list was provided to a family member for reading and his name should never have been read. It was a mistake, it should not have happened and we sincerely apologize.

That list is part of a Slate article titled, "How Many People Have Been Killed by Guns Since Newtown?" (The Atlantic Wire used data from the Slate list for our visualization of gun deaths.) As seen at right, the name Tamerlan Tsarnaev is included in the list, killed on April 19 in Watertown, Massachusetts. That Slate list, it should be noted, points to the Twitter account @GunDeaths as the source of its data. The Twitter account has only been updated once since March, indicating that Slate was taking over the account. A downloadable list at the Twitter account includes Tsarnaev's name.

Dan Kois, an editor at Slate, explained to The Atlantic Wire why Tsarnaev was on their list — an intentional inclusion.

The interactive is a tally of all the people who've been killed by guns since the Newtown shootings. So it doesn't differentiate between good guys and bad guys. We were studiously attempting to be as clear as possible that this was not victims of gun crimes … it was everybody that's been killed by guns since Newtown.

Tsarnaev was "by no means" the only person on the list shot by law enforcement during the commission of a crime, Kois said. He wasn't able to say how many of those listed fell into that category but noted that the complete list could be downloaded "if anyone wants to break it down."

But it's not only because Tsarnaev was a terrorist, shot by police officers, that one might think including him is inappropriate. The official cause of death on his death certificate attributes it to "gunshot wounds and blunt trauma" — meaning that Tamerlan wasn't necessarily even killed by gunfire. Instead, he was likely killed when his brother Dzhokhar ran him over. Kois said that didn't matter. "For the purposes of this interactive," he said, "killed-by-gun-plus-other-thing counts."

This article was updated to include Slate's response.