The NHL's Department of Player Safety wasted no time in making the announcement following today's game between the two teams. Hartman definitely got his leg behind DeBrincat's, and pushed him back with his arm. A classic slew-foot.
It's not really a surprise that this one is getting a hearing. It will be hard for Hartman to prove this was anything other than intentional, as you can clearly see him extending his leg to get behind DeBrincat's. The only question here seems to be how many games?