Gregory Beck, a member of the Brookfield school board, had written on Facebook his tribute to the "26 Acts" movement would be to give boxes of ammunition to his gun-enthusiast friends, the News-Times in Danbury reported.
The feel-good movement is dedicated to victims of the December 2012 shootings at Sandy Hook Elementary School in nearby Newtown.
At least 20 people over the span of two board meetings had asked Beck, 26, to step down over his comments. He apologized, but on Tuesday notified board chairman Scott McCarthy he was resigning, effective immediately.
The board will have to appoint a minor-party board member to fill Beck's seat.
Rob Gianazza, chairman of A Brookfield Party of which Beck was a member, said Beck reached the decision on his own.
"As far as A Brookfield Party is concerned, we never made any attempts to encourage or discourage him, other than to use his own judgment and make his own decision. I wish him all the best," Gianazza said.