Thursday marks five years since a gunman killed 20 children and six staff members at Sandy Hook Elementary School in Newtown, Connecticut.
So what's changed since then to prevent similar tragedies from happening in the future?
Examples of gun control laws have been rather scarce. Two major proposals right after the shooting couldn't pass the Senate.
Those proposals aimed to ban the sale of semiautomatic assault weapons and mandate background checks for gun shows and internet sales.
CBS noted in mid-2016 that Congress rejected over 100 gun safety measures during the previous five years.
The reaction to Newtown may be more apparent in classrooms and school hallways. An expert told ABC that schools have conducted exponentially more active shooter simulations and drills since Sandy Hook.
In the massacre's aftermath, then-President Barack Obama asked all schools to have comprehensive emergency plans.
But toward the end of his presidency, Obama told the BBC that failing to pass what he called "common sense gun safety laws" was his greatest frustration during his time in the White House.
