All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
In principle, all the behavior of Muslims should be interpreted in the best possible way and we should not think ill of them as long as this is possible. Accordingly, it is permissible, Allaah willing, to eat from this sheep for, in principle, it is supposed to be slaughtered for the sake of Allaah The Almighty and the Name of Allaah The Almighty is mentioned upon it. Allaah The Almighty Says (what means): {So eat of that [meat] upon which the Name of Allaah has been mentioned, if you are believers in His Verses.} [Quran 6:118]
However, if it turns out that it has been slaughtered for other than Allaah The Almighty, then it will be impermissible to eat from it, for Allaah The Almighty Says (what means): {He has only forbidden to you dead animals, blood, the flesh of swine, and that which has been dedicated to other than Allaah.} [Quran 2:173]
This is similar to the sacrifices people make at the graves of the pious and righteous people, which have become widespread nowadays.
Allaah Knows best.