The shootings in El Paso, Texas, and Dayton, Ohio, killed 31 people.
In the message, Booker said he was listening to Trump speak at the White House.
In the aftermath of mass shootings in El Paso, Texas, and Dayton, Ohio, calls are once again intensifying for Congress to pass gun control legislation, with many pointing to the political influence of the National Rifle Association as a main cause of inaction to address the epidemic of gun violence in the United States.
Both shooting suspects were US citizens, and federal officials are investigating anti-immigrant bias as a potential motive for the El Paso, Texas, massacre.
USA authorities said on Sunday that they are treating their investigation into El Paso massacre that left at least 20 people dead as "domestic terrorism" and a "hate crime". Republicans and Democrats must come together and get strong background checks, perhaps marrying this legislation with desperately needed immigration reform.
It was unclear how either of the shootings were related to immigration reform.
"We have to get it stopped".
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".
"Fake News has contributed greatly to the anger and rage that has built up over many years".
Gun culture is deeply rooted in America, and efforts to strengthen firearms regulations remain divisive even though mass shootings are commonplace.
Additionally, Trump directed the Department of Justice to seek and prioritize the enforcement of the death penalty in cases of hate crimes and mass shootings.
In December 2018, The Trump administration banned bump stocks, the attachments that allow semi-automatic weapons to fire like machine guns and were used during the October 2017 shooting massacre in Las Vegas.
Obama criticized the position of elected officials and members of the public who maintain that stricter gun laws will not stop a person determined to carry out mass violence, saying common sense measures can help prevent some killings and "save some families from heartbreak".
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. Less than a day later there was another mass shooting in Dayton that killed at least nine, while at least 27 others were injured.
Death toll in Texas shooting rampage rises
Patrick Wood Crusius, 21, of Allen, has been booked on capital murder charges and jailed without bond. A Texas prosecutor said the state will seek the death penalty against Crusius if he is convicted.
Koscielny in Bordeaux to finalise move
Emery has now identified France U21 worldwide Upamecano as their top defensive target, ahead of transfer deadline day. Arsenal are expected to be busy with ins and outs before the transfer window closes at 5pm on Thursday.