There's audio recording of Hind and her cousin Layan. It's pretty clear sounding from that, that it was IDF attacking, and that there was a considered element to what happened - this wasn't a case of a nervous soldier firing out of fear. This was a tank next to a civilian car. The audio recording suggests several pauses - a call with Layan, then one with Hind where there was a long enough pause in things that she reported she was aware the ambulance was getting close. Somebody waited before killing her.
The IDF knew Hind was in the car in that location, because they had that information as part of coordinating the ambulance response. It was known that the sole known surviving occupant of the car was a little girl.
The ambulance response had been coordinated with the IDF. IDF forces would either have known or been expected to have known that the ambulance was coming.
So, either the soldiers on the ground knew that there was a frightened, trapped child near them, with an authorised/coordinated ambulance on the way to retrieve her, and they chose to kill them all, or nobody bothered to share the information with the soldiers on the ground, knowing that there would be a likelihood of this outcome.
Both are horrible scenarios. Both are more likely than Hamas having the time, energy and interest to stage this.