"He shot dead" is incorrect by itself, even as a title. It needs to be "He shot dead <somebody>" ie. "He shot dead the mailman" (He killed the mailman with a gun)

Sometimes the author uses literary license which means that the author writes a book title or anything else and chooses not to use correct grammar. Sometimes this is to grab the reader’s attention. Or they are just trying to be creative and not follow writing conventions. I say ‘trying’ because I find it annoying. Here’s an example of literary license: It. Was. So. Exciting.

You can see that kind of titles in newspapers like 'journalists shot dead'. That mean they were shot. The language of titles has it's own peculiarities.