Read sentence ending with dot (.) without being interfered with a.m, p.m or middle names [duplicate]

I’m trying to read a sentence in between sentences that contains the word “gathering”.

[^rn.!]*(?i)gathering[^rn.!?]*[m.!?]+

Demo: https://regex101.com/r/eo8uTU/1

However, when the sentence also contains a middle name like R. or a.m or p.m, it fails to grab the entire sentence.

Hello there. Gathering for John R. Doe will be at 2 p.m. Don't miss out!

So, how can I grab the full sentence all the way to the final dot (.)?