What to do if (somehow involuntarily) one kills an animal? It happened to me during dinner, yesterday: I wanted to move a mosquito that was in my plate and accidentally killed it :(
What's the appropriate thing to do in such cases?
Is there any mantra to recite in order to have some benefit for the insect?
I'm asking this because I read about a mantra to be recited &quot;in front of your shoes&quot; so that, in case of walking on top of an animal, then it would be &quot;less bad&quot;.
But probably I'm totally wrong :)
In any case, I don't think my question is a duplicate of the guy who killed a mosquito on purpose because it was suffering.
I killed it because my intention was to move it from my plate, but I didn't pay much attention and did it wrongly.
Your concern for the mosquito recalls the limitless heart's release:

MN43:31.2: Firstly, a mendicant meditates spreading a heart full of love to one direction, and to the second, and to the third, and to the fourth. In the same way above, below, across, everywhere, all around, they spread a heart full of love to the whole world—abundant, expansive, limitless, free of enmity and ill will. They meditate spreading a heart full of compassion … They meditate spreading a heart full of rejoicing … They meditate spreading a heart full of equanimity to one direction, and to the second, and to the third, and to the fourth. In the same way above, below, across, everywhere, all around, they spread a heart full of equanimity to the whole world—abundant, expansive, limitless, free of enmity and ill will. This is called the limitless heart’s release.

Establishing such a mindfulness in every moment of the day benefits one and all.
The mosquito is gone, yet for those who remain, perhaps a gentle puff of air might be more skillful if needed for the next mosquito. And perhaps, even then, a simple letting be might suffice. Abide in the limitless heart's release and your heart will know what to do.