All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
It is obligatory on every Muslim to search lawful food; he should not be deceived by sign boards or by advertisement.
If you are sure that the meat is not slaughtered according to Islamic way, then it is prohibited. As regards the slaughtering by the People of the Book (Jews and Christians), if they are slaughtering according to Islamic way and do not kill the animal, then it is lawful.
For more benefit on meat of animals slaughtered by the People of the Book, please refer to Fataawa 82323, 82065, 81234, 393961, 330952, 82899 and 84072.
Allah knows best.