Driver was going under the speed limit, so I tried to pass them in a passing zone. They then sped up 20 MPH so that I couldn't pass them until a car was coming from the opposite direction. I tried to honk but they kept speeding, when I got back behind their car, they slammed on their brakes and then continued to drive below the speed limit. It seemed like they were attempting to cause a car accident. I reported their license plate number to the local police as soon as it happened, and now I'll be reporting it everywhere else I can online.