A gunman opened fire in a gay nightclub in Orlando early Sunday morning, killing at least 50 people and making it the deadliest mass shooting in American history.

It was a terrible, tragic event — and the 133rd mass shooting in 2016 alone. It was the 15th mass shooting in Florida this year, and the fourth in Orlando.

The nonprofit Gun Violence Archive (GVA) tracks mass shootings in the United States. And their data shows that there have been 76 days this year with mass shootings in the United States — and 88 days without. A total of 207 people have died in those incidents, including the known victims of the shooting on Sunday in Orlando.

Source: Gun Violence Archive Credit: Sarah Frostenson

GVA uses the FBI definition of a mass shooting, which is defined as a single event where four or more people are shot (not necessarily killed) and does not include the shooter in the tally. It's important to note, however, that there is not one universally accepted definition of what constitutes a mass shooting, and many methodologies differ from how GVA collects its data.

Some counts, like the one compiled by USA Today, only track mass killings, or events in which four or more people were killed. Mother Jones also maintains a database, which, like USA Today’s, only tracks events in which four or more people were killed, but Mother Jones excludes shootings related to "gang activity, armed robbery, or domestic violence." (GVA does not exclude shootings related to gang or domestic violence.)

Even so, its an important resource that underscores the prevalence of gun violence in America — and how frequently shootings that involve multiple people happen across the country.

Florida has had more mass shootings this year than any other state

There have been 15 mass shootings so far in Florida, which is more than any other state. GVA’s database shows two other states that have had more than 10 mass shootings this year: California has had 14 and Illinois has had 11.

Four of those shootings occurred in Orlando, including the shooting at the Pulse nightclub on Sunday. The other shootings were:

There were five mass shootings on February 20 alone

On February 20, 10 people died from mass shootings and 15 were injured — in five separate places.

This includes the February 20 shooting in Orlando mentioned earlier, where four women and a police dog were shot during a grocery store robbery. This was the same day as a shooting in Kalamazoo, Michigan that got national attention — and left six people dead.

A man in Tampa, Florida was killed early that Saturday morning in a bar. An Alabama man died in a drug-related shooting — and a Mississippi police officer also died, at the end of a six-hour standoff related to a domestic dispute.

Mass shootings are one part of America's gun violence problem

On the whole, regardless of differences in classification, deaths from mass shootings make up a small fraction of deaths from gun violence. The Centers for Disease Control and Prevention estimated that in 2013 alone, 33,636 people died in firearm deaths, or 92 people every day. But looking at 2013 data from the Mass Shooting Tracker, only 502 of those deaths — or 1.5 percent — were connected to mass shootings.

Most gun deaths in the United States (21,175 of 33,636 in 2013) are suicides. And most non-suicide deaths (11,208) are homicides. The rest are classified as accidents and police shootings. And while it's true that homicide rates have reached historic lows, no other developed country in the world has the same rate of gun violence as America. The US has nearly six times the gun homicide rate of Canada, more than seven times the rate of Sweden, and nearly 16 times the rate of Germany, according to UN data compiled by the Guardian.

This is not to say that Americans shouldn't care about mass shootings. But mass shootings are only one part of the equation in America's ongoing problem with gun violence.

You can see below a complete calendar of all mass shootings that have occurred in the United States, as well as a tally of all deaths from those events. And you can read more of Vox’s coverage of the Orlando shooting here.