Keep Factually independent
Whether you agree or disagree with our analysis, these conversations matter for democracy. We don't take money from political groups - even a $5 donation helps us keep it that way.
Fact check: What percentage of mass shooters in the US have been affiliated with right-wing extremism since 2004?
Executive Summary
The available materials do not provide a single authoritative percentage of U.S. mass shooters affiliated with right‑wing extremism since 2004; published analyses instead offer differing slices of related phenomena—extremist-linked mass killings, ideological motives across longer timeframes, and domestic terrorism deaths. Some sources point to a dominant role for right‑wing violence in recent domestic terrorism deaths, while others show smaller shares of mass‑casualty incidents explicitly linked to extremism or offer broader measures of ideological motivation; reconciling these requires careful attention to definitions, timeframes, and case selection [1] [2] [3].
1. How advocates framed the claim — big numbers, big implications
Advocates citing a high share of right‑wing involvement rely on aggregated domestic terrorism death data that attribute the majority of fatalities to right‑wing extremist violence since 2001, presented as evidence that most lethal extremist violence in recent decades stems from the far right. The September 2025 analysis noted a 75–80% share of domestic terrorism deaths tied to right‑wing actors, framing the phenomenon as disproportionately concentrated on the right and implying a substantial role for right‑wing affiliation among lethal attackers [3]. That framing uses fatalities as the metric, which amplifies incidents with high death counts.
2. Why those fatality‑based figures don’t equal “percentage of mass shooters”
Fatality counts and shooter counts measure different things: a small number of high‑death attacks can dominate death totals while representing few perpetrators, so a 75–80% share of deaths does not directly translate into the same share of shooters. The July 2023 and July 2024 studies show that extremist links are a minority or a portion of broader mass‑casualty and public mass‑shooter populations, with one study reporting more than 5% of mass‑casualty events tied to extremism for a recent window, and another finding roughly one‑quarter of public mass shooters across a long timeframe had extreme ideological interests [1] [2]. Differences in unit of analysis matter.
3. Timeframe and case definitions shift the picture dramatically
Sources differ on timeframes (2001, 2004, 1966–2023, 2018–2021) and on whether they count public mass shooters, mass‑casualty events, ideologically motivated attackers, or deaths from domestic terrorism. The July 2024 research assessed public mass shooters from 1966–2023 for ideological motivations, while the ABC News piece focused on 2018–2021 mass‑casualty events. The September 2025 piece aggregated domestic terrorism deaths since 2001. Any percentage claim about 2004–present depends critically on these methodological choices, which the supplied analyses explicitly vary [1] [2] [3].
4. Multiple studies point to an increase in right‑wing linked lethal violence, but not a clear shooter percentage
Several items indicate a rise in far‑right lethality: the 2025 analysis links most domestic terrorism deaths to right‑wing actors, and recent scholarship documents expanding far‑right mobilization pathways. However, none of the provided items gives a definitive percentage of shooters since 2004 with right‑wing affiliations, and one peer‑reviewed study finds ideological extremism present in about 25% of public mass shooters across decades, not specifically right‑wing proportion for 2004–present [3] [2] [4]. The evidence therefore supports increased right‑wing lethality without a clean shooter‑share figure.
5. Where the evidence leans and what it leaves out
The balance of supplied analyses leans toward right‑wing actors accounting for a large share of domestic terrorism deaths and highlights pathways to far‑right violence, suggesting a disproportionate lethal impact from right‑wing extremism in recent years. But the data leave out consistent coder protocols for ideological affiliation, clear inclusion criteria for “mass shooter,” and disaggregated counts by year since 2004. Those omissions prevent converting the qualitative pattern into a single, reliable percentage for shooters since 2004 [3] [4] [1].
6. How to responsibly interpret or report a percentage claim
A responsible statement about “percentage of mass shooters affiliated with right‑wing extremism since 2004” must specify metric (shooters vs. deaths), dataset, case definition, and time window. Using fatalities biases toward high‑casualty incidents; using event counts or perpetrator counts yields different numbers. The provided materials suggest that any high percentage claim without methodological anchors is overstated or ambiguous, because comparable, transparent counts for 2004–present are not present in the supplied sources [2] [3].
7. Bottom line and recommended next steps for clarity
The supplied analyses show clear evidence of rising far‑right lethal violence and significant right‑wing responsibility for domestic terrorism deaths, but they do not establish a single percentage of mass shooters affiliated with right‑wing extremism since 2004. To answer the question precisely, one needs a published dataset that defines “mass shooter,” enumerates perpetrators from 2004 onward, and codes ideological affiliation consistently; absent that, cite the differing metrics—75–80% of domestic terrorism deaths (fatality‑based) and roughly 25% of public mass shooters with ideological interests across 1966–2023 (shooter‑based)—and explain the methodological divergence [3] [2] [1].