US President Joe Biden urged Congress to ban assault weapons used in recent atrocities in Texas and New York.
56 lit candles were displayed down a lengthy corridor behind Biden to signify US states and territories suffering from gun violence.
"How much more devastation are we going to accept?" he questioned in an angry, near-whispered statement.
"We can't fail the American people again," he said, calling Republican senators' refusal to back stricter laws "unconscionable."
At a minimum, Biden argued, lawmakers should raise the age at which assault weapons can be acquired from 18 to 21.
He encouraged them to enhance background checks, restrict high-capacity magazines, require safe weapons storage, and hold gun manufacturers accountable for crimes committed with their goods.
"More school-age children have perished from weapons in the last two decades than police officers and soldiers combined. Consider, "said Biden.
Cross-party senators held talks Thursday on a package of gun regulations, despite Republican opposition.
Nine senators met this week to explore a response to the nation's deadly shootings, expressing confidence about modest adjustments.
The group has concentrated on school security, mental health care, and encouraging states to give courts "red flag" authority to temporarily confiscate guns from threat owners, a step Biden also called for.
As lawmakers debated how to respond to the killing of 10 Black supermarket customers in Buffalo and the school massacre in Texas that murdered 19 youngsters and 2 teachers, another incident occurred in Oklahoma.