“Code black” and “No blasters” sound very similar.

Linguistic breakdown:

/k/ and /n/ are both common obstruents
Then they both have /o͡ʊ/
There’s /db/ and /b/, but often, /db/ becomes /b/
Then there’s /læ/
/k/ and /s/ are common obstruents commonly mistaken for each other
The “ers” part is kinda quiet, especially on the second yell. Your brain probably thought “Code black”, went with it, and ignored the “ers”.

Those of you who are dank linguists, I know this wasn’t 100% perfect but it gets the point across.