The flags will remain at half-staff until sunset on Aug. 8.
Walmart issued a statement on the shooting at its El Paso, Texas location:
Several politicians also chimed in, offering thoughts and prayers, while others said that is not enough.
Former President Barack Obama issued a statement on the shootings on Monday afternoon.
"Michelle and I grieve with all the families in El Paso and Dayton who endured these latest mass shootings," the lengthy statement said. "Even if details are still emerging, there are a few things we already know to be true.
"First, no other nation on Earth comes close to experiencing the frequency of mass shootings that we see in the United States. ... Second, while the motivations behind these shootings may not yet be fully known, there are indications that the El Paso shooting follows a dangerous trend: troubled individuals who embrace racist ideologies and see themselves obligated to act violently to preserve white supremacy."
Obama's full statement can be read below.
The shooting also sparked a conversation about gun control. The hashtag #GunControlNow quickly became on trending topic on Twitter.