Have extremist groups on the far right or far left been more associated with mass killings in recent years?
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Executive summary
Data collected by multiple research groups and advocacy organizations show that far‑right extremists have accounted for the majority of recent U.S. extremist-linked mass‑killings and the deadliest incidents in the past decade, though some 2025 analyses report a recent uptick in far‑left incidents by count (not fatalities) for the first time in 30+ years (CSIS; ADL; PBS) [1] [2] [3]. Analysts stress the picture is volatile: far‑right attacks still caused far more deaths historically, while 2025 saw fewer far‑right incidents and a rise in low‑fatality left‑wing plots, making short‑term comparisons sensitive to definitions and highly influenced by a small number of mass‑casualty events [4] [5] [1].
1. The historical baseline: far‑right violence has driven most deaths
Across the last decade, multiple sources document that far‑right extremists were responsible for the majority of extremist‑linked fatalities in the U.S. — for example, one dataset showed 152 far‑right attacks since 2016 vs. 41 left‑wing, with 112 deaths from right‑wing attacks compared with 13 from left‑wing attacks over roughly the same span (Axios summarizing CSIS/other research; FiveThirtyEight’s earlier analysis) [4] [6]. The ADL likewise reports that white supremacists and other far‑right actors produced the lion’s share of extremist‑related murders in recent years, and that years with mass shooting sprees drive national totals [5] [2].
2. 2025 introduced a complex—yet narrow—shift in counts, not lethality
Several 2025 analyses found that left‑wing incidents outnumbered far‑right incidents in the first half of 2025 — a first in over 30 years — but the research authors and critics emphasize this was a rebound from an unusually low rate of right‑wing incidents and reflected many low‑fatality plots and attacks against hardened government targets rather than a surge in mass killings that produced large numbers of victims (CSIS; CSIS caveats) [1]. Critics and other analysts note that while counts rose, those left‑wing events resulted in far fewer deaths than the historically more lethal far‑right attacks, and that a single high‑casualty far‑right incident can rapidly change fatality tallies [7] [8] [4].
3. Definitions and small‑number volatility drive divergent headlines
Reports use different definitions — “attacks,” “incidents,” “mass killings,” and time windows vary — and because mass‑killing events are small in number but high in consequence, trends are volatile: a handful of mass shootings (e.g., Buffalo, El Paso, Tree of Life) account for a disproportionate share of extremist‑linked deaths, so declines or spikes hinge on prevention or occurrence of those events [9] [10] [11]. The Northeastern/AP mass‑killings database and public‑mass‑shooting catalogs produce different lenses on the problem, which explains why some outlets emphasize falling mass killings in 2025 while others highlight ideological patterns [12] [13].
4. Where targets differ: left actors vs. right actors
Researchers report that left‑wing perpetrators more often target government or law‑enforcement facilities — locations that tend to be hardened and thus less likely to produce mass fatalities — whereas far‑right attackers have frequently targeted civilian crowds, houses of worship, and racial or ethnic minorities, producing higher fatality counts when attacks succeed (CSIS; The Conversation; ADL) [1] [14] [2]. That distinction helps explain why left‑wing incident counts can rise without producing comparable death tolls.
5. Law enforcement disruption and prevention shape recent declines
Organizations tracking extremist murders say declines in extremist‑related killings through 2024 and part of 2025 partly reflect disruption of planned far‑right plots and fewer deadly far‑right mass‑killings — outcomes credited to investigative and preventive work — while isolated high‑casualty events remain possible and can reverse trends quickly (ADL; AP; Axios) [5] [15] [13].
6. Competing interpretations and political uses
Some political actors have seized on selective findings — counts vs. fatalities — to make sweeping claims about which side “causes more violence.” Analysts warn that emphasizing counts without noting lethality, or vice versa, can mislead public understanding and policy priorities; several critiques explicitly say rising left‑wing counts do not overturn the longer record of deadlier far‑right violence (PBS; Just Security; NPR) [3] [7] [8].
7. Bottom line for readers
Available, multi‑source reporting shows far‑right extremists have caused more mass‑killing deaths in recent years, even as 2025 brought an unusual rise in left‑wing incidents by count and an atypical dip in right‑wing incidents — a short‑term shift driven by small numbers, definitions, and the location and lethality of attacks [4] [1] [5]. Policymakers and the public should focus on both preventing plots and understanding that a single high‑casualty event can quickly reshape the landscape; researchers urge caution in drawing sweeping conclusions from a volatile, low‑N dataset [9] [12].
Limitations: sources cited vary in methodology, time frames and definitions; available sources do not mention a single unified, universally accepted dataset that settles the question for all time [4] [1] [12].