(CNN) - Diverging from the generally non-political college sendoff, New York City Mayor Michael Bloomberg, a gun-control advocate, Saturday tore into members of Congress for failing to pass background check legislation.
Giving a commencement address at Kenyon College in Ohio, Bloomberg recounted a shooting last year by a 17-year-old who opened fire at an Ohio high school, killing three and injuring others.
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"It was national news - for a day or two," said Bloomberg, according to prepared remarks. "Then came mass shootings in Pittsburgh, Miami, Oakland, Tulsa, Seattle, Wilmington, Aurora, Milwaukee, Texas A&M, Minneapolis, Brookfield, Portland."
"After each one, those in Washington just shrugged."
"Then, Sandy Hook Elementary School in Newtown, Connecticut. Twenty children, six faculty members all gunned down," Bloomberg continued, noting the push by President Barack Obama and various members of Congress to pass gun-control legislation.
One ensuing measure, authored by Democratic Sen. Joe Manchin of West Virginia and Republican Sen. Pat Toomey of Pennsylvania, fell short of the 60-vote threshold needed to move forward in the Senate.
The legislation would have expanded background checks on firearms sale to online and private sales, excluding those between family members. A separate failed proposal called for banning some semi-automatic weapons modeled after military assault weapons.
Bloomberg said members of Congress lacked "the courage to stand up to the increasingly extremist view of the NRA's Washington lobbyists," pointing to concern from some lawmakers who voted against the measure, including Democrats with a large number of Republican constituents, of political retaliation from gun rights advocates.
Tying the address back to Kenyon, Bloomberg quoted college alumnus and former President Rutherford B. Hayes, who said, "He serves his party best who serves his country best."
"Instead, we have a federal law that prohibits criminals and the mentally ill from buying guns - and we have a Congress that doesn't have the courage to enforce it through a comprehensive background check system," Bloomberg told graduates.
After rattling off a number of gun-related death statistics, Bloomberg indicated that though he had given up on Washington, he had not given up on the next generation.
"I believe we will win - sooner or later. Because I believe in all of you," he said, "Your generation - more than any other, at least since the 1960s - is reshaping society in fundamental ways by making your values known and your voices heard."
CNN's Steve Brusk and Dana Davidsen contributed to this report.