Good grief, why wouldn't you call 911 if your residents were stuck in 100+ degree temperatures for 3+ days? It's basic common sense and human decency, which isn't something that you need a nursing license to possess.
However, this isn't only on the nurses - this is also on the DON, administrator, medical director, etc. Sounds like lots of balls were dropped and unfortunately innocent people paid the ultimate price.
Look at how quickly things happened once the emergency authorities were finally alerted on the timeline provided. People never need have died if only one staff member had reached out for help earlier.