Grok said:
Data on mass shootings involving transgender perpetrators is limited and varies by definition and source. The Gun Violence Archive (GVA), which defines a mass shooting as four or more people shot (excluding the perpetrator), recorded over 4,400 mass shootings in the U.S. from 2013 to 2023. According to GVA's Executive Director Mark Bryant, fewer than 10 of these incidents involved transgender suspects, translating to roughly 0.11% of the total.
The U.S. Secret Service National Threat Assessment Center (NTAC) analyzed 173 mass attacks (harm to three or more people in public) from 2016 to 2020, finding that 3 attackers (2%) were transgender, all assigned female at birth but identifying as male at the time of their attacks.