I was experimenting what entities could be held by leads, and was flying through the air holding a rabbit, and just for fun decided to drop the poor thing down to the ground and kill it. but it wouldn't release the rabbit. I then dropped the lead out of my inventory, but still the rabbit was attached, as well as the lead, and my right arm was not visible. I flew around some more and went up and down and the rabbit was still attached. it was only when i touched the ground the rabbit fell of. I have managed to replicate this several times and it has the exact same result.
In the first image you can see me holding a rabbit on a lead in mid air, as normal. But in the second image, you can see, even though I have dropped the lead, the rabbit remains suspended in the air. as soon as the rabbit touches the ground the action that would have been performed after the rabbit falling gets triggered and the rabbit dies.