"Omar Mateen, the shooter who killed 49 people at a nightclub in Orlando, Florida, in 2016, was registered as a Democrat in 2006. He voted in the Florida primary in 2016, according to reporting from Politico."
"In 2017, 66-year-old James Thomas Hodgkinson shot and injured six people at a congressional baseball game in Virginia — nearly killing House Majority Whip Steve Scalise. Hodgkinson volunteered for the presidential campaign of Democrat Bernie Sanders and apparently targeted the Republican team."