Pelosi calls for 'balance' between free speech and safety after Buffalo shooting

House Speaker Nancy Pelosi said Sunday that social media companies have to address and track down extremism on their platforms, after a gunman who reportedly espoused white supremacist ideology opened fire at a Buffalo, New York, supermarket on Saturday, killing at least 10.

Among the 13 victims shot, 11 were African American and two were white, authorities said.

"There has to be vigilance," Pelosi, D-Calif., said on ABC's "This Week." "People have to alert other authorities if they think that someone is on a path to domestic terrorism, to violence of any kind."

Investigators are looking at multiple online postings that may be associated with the shooter, 18-year-old Payton Gendron, that include praise for South Carolina church shooter Dylann Roof and the New Zealand mosque shooter Brenton Tarrant, sources told ABC News.

"Obviously you have to balance the free speech issues," Pelosi said. "Freedom is so important to us but that freedom also carries public safety with it and we have to balance that."

The California Democrat said her party in Congress is "of course trying to do something about gun violence" but noted that efforts to address mass shootings on Capitol Hill have fallen short in the Senate, where Republicans have opposed gun control measures, making it impossible for Democrats to advance legislation over the 60-vote threshold in the chamber.