"We can not let those killed in El Paso, Texas, and Dayton, Ohio, die in vain".
He added, "It's time for the overwhelming majority of Americans of goodwill, of every race and faith and political party, to say as much - clearly and unequivocally".
In his statement - one of only a couple of public proclamations he's made since leaving office in early 2017 - the former two-term Democratic president said he and former first lady Michelle Obama are grieving with all the families affected by the massacre in El Paso and another mass shooting in Dayton, Ohio that killed nine people.
As the Sunday exchange with journalists went viral, the presidential candidate - on Twitter and in interviews - repeated his indictments of Trump and his exasperation with those hesitant to link the president to the racism potentially behind the shooting. Authorities are still investigating but believe the suspected gunman wrote an anti-immigrant manifesto posted online before killing 22 people and wounding dozens at a busy shopping center. He seemed to abandon his latest idea of linking gun control legislation to immigration policy just a few hours after proposing it.
The mayor of El Paso said at a news conference that Trump would visit the city Wednesday, though some local lawmakers and others signaled opposition, and the Federal Aviation Administration advised pilots of a presidential visit to Dayton. "We can not allow him to get off scot-free just because he gave a speech here today".
Obama denounced language from "leaders who demonize those who don't look like us, or suggest that other people, including immigrants, threaten our way of life, or refer to other people as sub-human, or imply that America belongs to just one certain type of people".
In his message posted Monday afternoon, Obama did not mention Trump by name, but his intended target was clear.
"Fake News has contributed greatly to the anger and rage that has built up over many years".
And Trump himself has reneged on previous pledges to strengthen gun laws.
After other mass shootings he called for strengthening the federal background check system, and in 2018 he signed legislation to increase federal data sharing. "At my direction, the Department of Justice banned bump stocks", Trump said.
House Speaker Nancy Pelosi and Senate Democratic leader Chuck Schumer said Monday that Trump should push the GOP-controlled Senate to take up the House's background check bills.
However, Trump drew criticism for mixing up the location of the Dayton shooting with another OH city in the same speech.