Noticing that they were no longer returning fire, he stopped shooting and peeked around the corner.
Realizing that they were no longer returning fire, he stopped shooting and peeked around the corner.
Noticing that they weren't returning fire anymore, he stopped shooting and peeked around the corner.
Realizing that they weren't returning fire anymore, he stopped shooting and peeked around the corner.
Are "noticing" and "realizing" close to interchangeable in this context? And the same with "no longer" and "anymore"?
I have written the first sentence, is that the one which sounds more natural to you as well?