Walmart confirmed the move in a statement to Vice, saying it was "out of respect" for the victims of the El Paso and Dayton shootings, and that this "does not reflect" a change in the actual game catalog. You can still buy Call of Duty, you just won't see it advertised.
At the same time, ESPN2 delayed its August 11th airing of the Xgames' Apex Legends EXP Invitational for similar reasons. Kotaku sources understood that the competition would now air on October 6th, October 15th and October 27th.
While both moves were made out of sensitivity, they could still be problematic by giving credence to the unsupported claim that video games cause violence. Multiple studies have shown that these titles don't lead to violent behavior, and that proponents of restricting violent game sales have historically used it to distract from questions about gun control and gun culture. Walmart is still selling guns, although CEO Doug McMillon hinted at openness to change with promises of "thoughtful and deliberate" responses to issues raised by gun violence. The video game and movie display changes may just be the start of a larger strategy shift.