The reality star, 41, who has four children, said “weapons of war” should not be available to the general public and that lawmakers should be “pushed” to enact legislation more suited to modern times.
In a lengthy post on social media, Kardashian also highlighted issues with the legal age at which firearms could be bought in the US and how mental health, racism and “deep-seated hatred” all played a role in mass shootings.
At least 19 children and two adults have been reported dead after gunman Salvador Ramos, 18, opened fire at Robb Elementary School in US city of Uvalde, Texas, on Tuesday.
“There is no excuse and no justification for what happened yesterday,” Kardashian wrote.
“The current laws in our country around gun control are not protecting our children. We have to push lawmakers to enact laws that are fitting in today’s world.
“Semi automatic weapons, assault weapons, weapons of war, should not be legally sold or owned by American civilians.
“They should be banned. Period.”
Kardashian pointed out that the ages of those involved in previous shootings, including in Parkland, Florida, Buffalo, New York, and now Texas were all under the age of 21 and yet had reportedly purchased their weapons legally.
“Someone who is not old enough to buy alcohol should not be allowed to purchase a firearm,” she said.
“There is no world in which an 18-year-old needs a semi automatic weapon, or any weapon, and no world in which the outcome can be anything other than tragic.
“As I even type these words I am seriously dumbfounded that this is something considered normal, acceptable and legal.”
She continued: “We can’t accept this as normal any more.
“It’s not normal for a teenager to kill children. It’s not normal for our kids to be practicing active shooter drills in schools.
“I’m not numbed by it. I will never be numbed by it. We can’t accept it.
“Words can’t express my heartbreak for the parents whose babies didn’t come home from school yesterday.”
Kardashian has previously spoken out on both political and high-profile US legal cases, and recently passed her first year law students’ examination, known as the “baby bar”.
She joined scores of other famous faces including Matthew McConaughey, James Corden, Taylor Swift, Amy Schumer and Chris Evans who have expressed their “rage and grief” in the wake of the tragedy.