https://www.gao.gov/assets/690/683984.pdf

Since September 12, 2001, the number of fatalities caused by domestic
violent extremists has ranged from 1 to 49 in a given year. As shown in
figure 2, fatalities resulting from attacks by far right wing violet extremists
have exceeded those caused by radical Islamist violent extremists in 10
of the 15 years, and were the same in 3 of the years since September 12,
2001. Of the 85 violent extremist incidents that resulted in death since
September 12, 2001, far right wing violent extremist groups were
responsible for 62 (73 percent) while radical Islamist violent extremists
were responsible for 23 (27 percent). The total number of fatalities is
about the same for far right wing violent extremists and radical Islamist
violent extremists over the approximately 15-year period (106 and 119,
respectively). However, 41 percent of the deaths attributable to radical
Islamist violent extremists occurred in a single event—an attack at an
Orlando, Florida night club in 2016 (see fig. 2). Details on the locations
and dates of the attacks can be found in appendix II.