The bloodshed inside a Louisiana movie theater on Thursday night fits a certain, distressingly familiar pattern: A crowded public place, a lone gunman and a sudden burst of violence. At least two people were killed, and nine others wounded, before the gunman took his own life, police said.

If it seems like these kinds of things occur more often than they used to, that isn’t your imagination. A study released by the FBI last year found that active shooting incidents (not mass killings or shootings, which we will explain in a moment) are on the rise.

The FBI studied a total of 160 “active shooter” incidents between 2000 and 2013, finding that an average of 11.4 such shootings occurred each year. Over the first seven years, an average of 6.4 shootings occurred each year; over the last seven years of the study, 16.4 incidents took place.

It is important to pause here and note what this study examined and what it did not. Active shooting incidents are generally defined as someone “actively engaged in killing or attempting to kill people” in a populated area, the study said; these typically, but not universally, occurred in confined spaces like schools, businesses and theaters.

The FBI study did not focus on mass killings or shootings, nor did it explore every gun-related incident (ignoring things like gang-related violence or a person committing suicide in a public place). So the study did not say that mass killings or shootings — defined by the federal government as incidents where three or more people are killed “in a single incident” — were on the rise.

This is the subject of some debate. An investigation by Mother Jones found that mass shootings were on the rise, while a 2013 study by criminologists James Alan Fox and Monica J. DeLateur of Northeastern University found that while there are nearly 20 mass shootings a year in the U.S., this particular number has not increased. “There have been several points in time when journalists and others have speculated about a possible epidemic in response to a flurry of high-profile shootings,” they wrote. “Yet, these speculations have always proven to be incorrect when subsequent years reveal more moderate levels.”

The 2013 study did include gang violence and other incidents not counted by the FBI or Mother Jones, though, which other researchers have said gets away from the types of shootings we have seen in Newtown, Aurora and elsewhere. An analysis from researchers at the Harvard University School of Public Health and Northeastern University using the Mother Jones data found that mass shootings are indeed occurring more frequently, focusing on attacks with at least four victims and “in which the shooter and the victims generally were unrelated and unknown to each other,” they wrote.

There is also some disagreement over what, precisely, fits the definition of a mass shooting or a mass killing. While the federal government deems mass killings to have three or more victims, this obviously leaves a bit of a gap between mass killings and active shooter situations. The shooting in Lafayette, La., would appear to highlight this gulf.

Take that FBI study on active shooting incidents, which found that 40 percent of the shootings they looked at had three or more people killed. In other words, the majority of the active shooter situations were not mass killings. During some of these situations, the gunmen (and they were almost exclusively men) wounded people but did not kill anyone. Other incidents, like the 2008 shooting inside a Tennessee church that killed two people and injured seven others, would not fit the definition of mass killings. And the Lafayette theater shooting currently does not reach the mass killings threshold, because the gunman killed two people and wounded nine others.

One crowd-sourced project called the Mass Shooting Tracker found 204 mass shootings so far this year, though it expanded the definition to include incidents where four or more people are wounded, not just killed (based on the FBI’s older description of a mass murder as having at least four victims).

This project gives some idea of the scope of daily gun violence in the United States, although it also points to the bigger questions about how, exactly, we define mass shootings. The Mother Jones investigation and the FBI study, for example, both excluded instances deemed to be “domestic” in nature, which generally occurred in residences and involved someone killing family members. However, the Mass Shooting Tracker includes a Georgia man who allegedly shot and killed five people, including his wife, mother-in-law, father-in-law and step-daughter. It also includes the shooting of five men in the Bronx last month, all of whom were wounded and survived, which would not fit the mass killing definition.

Meanwhile, the FBI study did provide some other common factors seen in active shooter situations that have occurred across the country. Nearly half of the shootings occurred in commercial businesses, while the second-most-common locations were schools or related environments (like school board meetings).

Nearly half of the active shooters the FBI studied killed themselves, almost all of them doing so at the scene, as police say occurred in Lafayette. Far, far less often, someone carries out a shooting spree in a public place and goes on to face trial, like the gunman convicted last week of shooting and killing 12 people and wounding another 70 inside an Aurora, Colo., movie theater.

The third anniversary of that shooting occurred on Monday, just three days before the gunfire inside Lafayette’s Grand 16 theater. The trial has been marked by emotional, fraught testimonies recalling the horrific situation inside that movie theater during a screening of “The Dark Knight Rises.” On Thursday afternoon, jurors inched closer to considering a death sentence for that gunman. A few hours later and about 1,100 miles away, moviegoers in another darkened theater were scrambling for their lives as gunfire erupted once again.