Bloomberg group sorry for reading Boston bomber's name

(CNN) -- The group pushing for tighter restrictions on guns that's partly funded by New York City Mayor Michael Bloomberg apologized Wednesday after accused Boston bomber Tamerlan Tsarnaev's name was read at an event memorializing gun victims.

Noting they were using a list compiled by of people killed by guns since December's school shooting at Sandy Hook Elementary School, Mayors Against Illegal Guns said in a statement Tsarnaev "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."

The reading of names, which occurred in Concord, New Hampshire, was meant to show "the very real and personal cost of gun violence, and to help prevent more names from being added to a list that tragically grows longer each day," the group said.

Tsarnaev, along with brother Dzhokar, is suspected of planting bombs at the finish line of April's Boston Marathon. The attack left three people dead and wounded scores more. After a city-wide manhunt, Tamerlan Tsarnaev was killed in a shootout with police, while Dzhokar was captured and currently awaits trial.

Mayors Against Illegal Guns has actively campaigned for new gun control measures in the months since the December school shooting in Newtown, Connecticut. They've specifically gone after senators who voted against a bipartisan measure expanding background checks on gun sales, including New Hampshire's Kelly Ayotte.

The event in Concord Tuesday was part of the group's "No More Names" bus tour marking the 6 month anniversary of the school shooting. After the New Hampshire Union Leader first reported the accused Boston bomber's name was read at the event, Republicans in the state quickly decried the pro-gun control group.

"Tamerlan Tsarnaev was a murderous terrorist and a cold-blooded killer," said Jennifer Horn, the chairwoman of the New Hampshire GOP. "It is outrageous that Mayor Bloomberg's gun control group is so radical and out of touch with New Hampshire values that it believes this monster should be labeled as some kind of victim."