At least 19 children have died in the deadliest school shooting in nearly a decade, after an 18-year-old gunman opened fire at an elementary school in Texas on Tuesday.
A teacher was also killed in the attack, while a Border Patrol officer killed the shooter.
The attack happened just 10 days after a deadly shooting in Buffalo, New York, which killed 10 people.
The school shooting has sparked yet another fierce debate into gun control in the United States where regulations on purchasing firearms are relatively relaxed.
Here's everything you need to know about gun possession in America.
How does US gun control law work?
At a country-wide level, the Second Amendment in the Constitution is the well-known part of law enshrining the "right of the people to keep and bear arms."
Federal laws set out who is exempted from this general right to have a gun.
They restrict the sale of firearms to fugitives, people classed a danger to society and anybody involuntarily committed to a mental institution, and those with certain criminal convictions.
State law governs matters such as whether firearms must be concealed or not.
How old do you need to be to buy a gun?
Federal law requires someone to be at least 21 to buy a handgun from a licensed dealer, but only 18 in most places to buy a so-called "long gun".
Long guns are firearms with a longer barrel including shotguns and rifles.
Some states allow teens to buy or purchase long guns without parental consent, with some exceptions.
Only a few states have imposed stiffer age restrictions, requiring someone to be at least 21 before they can purchase a long gun.
In Texas, there is no minimum age to own a fire arm, although the state generally prohibits someone selling, renting, or giving a gun to someone under 18. However, this means that a child can legally be given a gun with their parents’ permission.
The younger age for long guns dates back to the 1880s.
How many people own firearms?
According to the Small Arms Survey of 2011, there are an average of 88 guns per 100 people in America.
On average, more than 13,000 people are killed each year in the United States by guns.
