The country superstar was onstage performing at the Route 91 Harvest music festival when the gunfire began.
"Over the last 24 hrs I have gone through lots of emotions," he said in a message posted on his official Instagram account Tuesday. "Scared, Anger, Heartache, Compassion and many others."
Authorities are still investigating what caused 64-year-old Stephen Paddock to open fire on the concertgoers from the 32nd floor of the Mandalay Bay Resort and Casino.
Aldean said in his posting that he doesn't understand "why a person would want to take the life of another."
"Something has changed in this country and in this world lately that is scary to see," he said. "This world is becoming the kind of place i am afraid to raise my children in."
"At the end of the day we arent Democrats or Republicans, Whites or Blacks, Men or Women," he added. "We are all humans and we are all Americans and its time to start acting like it and stand together as ONE!"
The singer also offered his condolences to the victims and ended his note with an appeal.
"Just know u all are in my heart and my prayers as we all go through this together," Aldean wrote. "Time to come together and stop the hate! #stopthehate #prayforlasvegas."
Read More: Jason Aldean addresses his anger and fear after Vegas tragedy