Since the tragedy in Uvalde, there have been other incidents of gun violence across the country in which a gunman shot multiple people.

Among those incidents: Four people were killed in a Tulsa, Oklahoma, medical center on June 1. One person was killed and seven were injured at an Oklahoma Memorial Day festival on May 29. Three people were killed and at least 11 people were injured in a popular area in Philadelphia on June 4.

Now, politicians are calling to attention how frequent gun violence is.

In a June 2 plea to the legislative branch to act on gun violence, President Joe Biden said, "Since Uvalde, just over a week ago, there have been 20 other mass shootings in America, each with four or more people killed or injured."

Sen. Chris Murphy from Connecticut, who gave an impassioned speech asking Congress to do something in the wake of the shooting in Uvalde, tweeted: "FYI this isn't stopping. There have been 18 mass shootings SINCE Uvalde. You need to know this. Because it's not going to stop until we do something."

Murphy followed with descriptions of some of the shootings and concluded with a final plea for readers to call their representative and senator.

Murphy highlighted this again on June 4: "Your morning reminder that in the 10 days since Uvalde, there have been 20 more mass shootings in the United States. In those 20 massacres, 91 were shot and injured and so far, 19 died."

PolitiFact Texas looked into some of the data sources for gun violence and how different organizations define mass shootings.

Murphy's office said his source was the Gun Violence Archive, a nonprofit that gathers data from 7,500 law enforcement, media, government and commercial sources to provide real-time, unbiased data on gun violence.

The archive said it is independent and is not designed to be an advocacy group. Gun violence incidents include murder/suicides, hate crimes, domestic violence, police action, accidents, brandishing guns and more.

The Gun Violence Archive defines gun violence as events that result in death, injury or threats involving firearms.

It defines mass shootings as incidents in which four or more people were shot in a single event at the same general time and location, not including the shooter. It defines a mass murder as four or more people killed in a single event at the same general time and location, not including the shooter.

The FBI defines "mass murder" as four or more murders during the same incident, with no specific time period between the murders. The federal government's Congressional Research Service defined "mass public shooting" and "mass murder" as at least four or more fatalities, regardless of injuries, in a 2015 document. And a 2013 federal mandate to investigate mass shootings in response to the Sandy Hook Elementary School shooting defined "mass killings" as three or more killings in a single incident.

Alex McCourt, director for legal research at Johns Hopkins Center for Gun Violence Solutions, said there is no legal definition for mass shooting.

"These definitions are important because they affect the kind of research findings that we might have," McCourt said. "How we define this will definitely affect how we measure whether certain laws are effective at reducing the incidents of mass violence, and will also affect policy and laws, and how we understand what new laws might be effective or what new laws might be necessary."

Everytown For Gun Safety defines a mass shooting in which four or more people are killed with a firearm, not including the shooter.

McCourt said there's also discussion about whether mass shooting is specific to indiscriminate violence, where a shooter fires a gun at random in public, or whether the definition includes a shooting at home or in an office where the shooter knows everybody.

"This is absolutely a continuing debate about what the definition should be," McCourt said.