The definition is evolving, for the better in my opinion. The below paper describes some thoughts in the realm which seek to develop a more inclusive definition.

Mass outcome or mass intent? A proposal for an intent-focused, no-minimum casualty count definition of public mass shooting incidents

https://jmvr.org/wp-content/uploads/2022/09/A-Proposal-for-an-Intent-Focused-No-Minimum-Casualty-Count-Definition-of-Public-Mass-Shooting-Incidents-Greene-Colozzi-Silva.pdf

First, researchers should expand their victim count inclusion criterion to gain valuable insight for public mass shooting prevention, intervention, and harm mitigation. The proposed definition of public mass shootings highlights mass intent instead of the completion of the shooting. Datasets with minimum victim counts are only including cases that occurred in the absence of mitigating situational factors, like fast intervention or strong situational crime prevention. There is always the potential for the environment and the situation to influence the incident outcome, and open-source scholars implementing a minimum casualty criterion might be systematically excluding cases characterized by mass intent and protective environments. Not only does this affect comparisons of environmental and mitigation factors, but it is an especially problematic source of selection bias for scholars aiming to understand the warning signs, behaviors, and psychosocial profiles of public mass shooting perpetrators.

Second, we advocate for scholars to use the current public mass shooting definition and completed, attempted, failed, and foiled outcome terminology. Critics may argue that our proposed definition more so aligns with an active shooter incident than a public mass shooting. However, we believe that it is beneficial to combine these two types of public gun violence involving random/symbolic victims into a single public mass shooting concept differentiated by outcomes. This will not only strengthen the rigor of empirical research, but also reduce public confusion. Currently, the mass media and general public are familiar with the phrases “public mass shooting” and “active shooting”, and understand both to be incidents of public, predatory gun violence committed by a highly motivated offender. We believe our definition, with its careful distinction between foiled, failed, attempted, and completed outcomes, could address some of the “mass confusion” (Fox & Levin, 2022) regarding public mass shootings.

Critics may argue that our proposal for an intent-focused, no minimum casualty count definition could contribute to journalistic abuse and further public confusion or concern. For comparison, after high-profile public mass shootings, media outlets often cite the number of mass shootings in America using the Gun Violence Archive and Mass Shooting Tracker data – which includes all mass shootings (i.e., felony and family), not just public mass shootings (Silva & Greene-Colozzi, 2019). The media thereby conflates all mass shootings with public mass shootings in the public consciousness. We do not want a consequence of this proposed public mass shooting definition to be the media’s inflation of the problem, given the increased number of incidents included in future research and datasets using this definition. To this end, we stress the importance of researchers using the completed public mass shooting terminology when referencing traditionally considered incidents - involving four or more fatalities – in research and during media interviews. In other words, like the usage of public mass shootings - which has recently become more popular in media usage - we are attempting to also incorporate completed public mass shootings into popular consciousness, to address public confusion and concerns.

Edit: I should add I have no beef with the GVA, and I don’t really think the flack it gets in this thread is warranted, but in this context the distinction I think can help. This is by no means GVA’s fault, terms evolve.