Right-wing extremists are turning cars into weapons, with reports of at least 50 vehicle-ramming incidents since protests against police violence erupted nationwide in late May.

At least 18 are categorized as deliberate attacks; another two dozen are unclear as to motivation or are still under investigation, according to a count released Friday by Ari Weil, a terrorism researcher at the University of Chicago’s¬†Chicago Project on Security and Threats. Weil has tracked vehicle-ramming attacks, or VRAs, since protests began.