The driver is an Armenian guy with a criminal record who is pissed at Turkey (the country). He wanted to kill Turks, saw a school class, which in Berlin is mostly Turkish kids, hit the gas an run them over killing one of the two teachers and injuring the rest along with other passersby. The police found a manifesto inside the car which is probably never going to be released and in which he supposedly rants about Turkey. In the second video here you can see the citizen arrest of the guy (fat guy in yellow t-shirt): https://jungefreiheit.de/politik/deutschland/2022/amokfahrt-berlin/ You can hear him asking for help. The guy filming (Turk or Arab) tells him he's an idiot and almost killed two persons, then he adds "he's a Gypsy or Romanian and he accelerated".