The tragedy at Pulse nightclub in Orlando, Florida has the highest death toll for a mass shooting in the recent history of the United States.
Shortly after the attack, the gun control debate flared up again.
"This massacre is therefore a further reminder of how easy it is for someone to get their hands on a weapon that allows them to shoot people at a school, or a movie theatre, or a church or a nightclub," President Barack Obama told media.
He also stated that Congress has the opportunity to change this, and to make such weaponry harder to acquire, adding: "To actively do nothing is a decision as well."
Republican presidential presumptive nominee Donald Trump took to Twitter to demand Mr Obama resign for not mentioning "radical Islamic terrorism", and to urge toughness and vigilance.
The US has a rate of gun violence considerably higher than any other developed country. According to the Centers for Disease Control and Prevention, there were more than 33,000 firearm-related deaths in the US in 2013.
The US is not the only country debating gun control. But it is perhaps the only one where many citizens see the gun ownership as being a crucial part of their nation's identity.
The Second Amendment
The US Constitution was signed in 1787 and is the supreme law of the United States.
The first ten amendments to the Constitution are known collectively as the Bill of Rights. Ratified in 1791, they offer specific protections of individual liberty and justice, and place restrictions on the powers of government.
The Second Amendment states the following: "A well-regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."
But exactly what that means is the subject of intense debate.
Pro-gun advocates insist it means every citizen should be entitled to own and carry just about any sort of firearm available, while gun control advocates say it was written in a very different time when the individual states had much more reasonable fears about the federal government.
Some legal experts within the US argue that private gun ownership isn't protected by the Second Amendment at all.
US citizens have a diverse range of opinions on the meaning of the Second Amendment. While the number of individuals who oppose all gun control laws are a minority, they are often more passionate about the issue than the supporters -- and they are backed by a very powerful political lobby.
Pro-gun rights protesters in Washington in January, 2013 (Reuters)
The National Rifle Association of America (NRA) is a non-profit organisation founded in 1871.
For much of its history, it was more of a sporting club than a lobby group, but it has been a serious political force against gun control since 1975, when members became worried legislative reactions to gun violence would ultimately result in the government's seizure of all firearms.
Since then, the NRA has strictly opposed gun control -- including the banning of military-style assault weapons, the introduction of background checks on firearms buyers and the creation of a national database of firearm purchases.
The firearm-owning population is a large and active constituency, particularly among Republicans. Getting on the wrong side of the NRA is a serious concern for conservative politicians and media.
The NRA has yet to make a statement on the Orlando massacre. Following other recent mass shootings, the organisation has generally remained silent for a few hours or even days before responding.
The NRA's responses to such tragedies tend to emphasise a need for more firearms rather than less, arguing that if more people were armed in such situations, they would be brought to an end more quickly and with less loss of life.
The NRA's power and influence has pushed many US legislators away from gun control measures, particularly at the national level and in Republican states, even though these measures have been successful in other countries and are often supported by the current president.
Donald Trump at the NRA annual meeting in Louisville, Kentucky, May 20, 2016 (Reuters)
During his first term in office, President Obama did not call for any major new restriction on guns or firearm owners. Instead, he urged authorities to enforce the state and federal laws already in place.
The NRA criticised his presidency nonetheless, calling him "the most anti-gun president in American history" and warning that "If [he] wins a second term in office, our Second Amendment freedom will not survive".
Mr Obama made reducing gun violence a central theme of his second term in office after the Sandy Hook mass shooting in December 2012.
In early 2013, he signed 23 executive orders and outlined a series of sweeping proposals. He called for mandatory criminal background checks on firearm purchasers and several other measures, including a ban on assault weapons and high-capacity magazines.
This year, Obama announced new executive actions extending background check requirements to more firearm sellers and compared the struggle for "common-sense gun reform" to women's suffrage and other civil rights movements.
While announcing the 2016 executive actions, Obama noted that many of the actions he's calling for can only be imposed through legislative action -- that must come from US Congress, which has consistently opposed and even blocked gun control bills.
"Congress still needs to act," Obama said at the time. "Because once Congress gets on-board with common-sense gun safety measures, we can reduce gun violence a whole lot.
"Until we have the Congress that's in line with the majority of Americans, there are actions within my legal authority that we can take to help reduce gun violence and save more lives."
President Obama during a live town hall event on reducing gun violence hosted in Fairfax, Virginia January 7, 2016 (Reuters)
What about the next president?
When he announced his candidacy for the presidency, Mr Trump said he fully supports the Second Amendment right to bear arms.
The NRA has officially endorsed Mr Trump and invited him to speak at its national convention in May.
There, he told members he "will not let you down".
"The Second Amendment is under threat like never before," Mr Trump told the crowd.
"Crooked Hillary Clinton is the most anti-gun, anti-Second Amendment candidate ever to run for office."
Democratic presumptive presidential candidate Hillary Clinton is in favour of "common-sense reforms" including "comprehensive background checks and closing loopholes" that allow firearms to fall into the wrong hands.
"I don't know how we keep seeing shooting after shooting, read about the people murdered because they went to Bible study or they went to the movies or they were just doing their job, and not finally say we've got to do something about this," says Ms Clinton.
Activists protest against gun violence on the third anniversary of the Sandy Hook mass shooting, outside the NRA headquarters (Reuters)
The gun control debate has received a great deal of media coverage during the second term of the Obama presidency, currently in its twilight.
This week's tragedy in Orlando, the latest in a series of high-profile mass shootings in the US along with the ever-popular discussion of terrorism, mean the debate will likely also be a theme in the first term of the next presidency.
In the meantime, the Unites States continues to lead the developed world in gun violence statistics by a horrifying margin.