That's at the high end of the re-hydration range, but you are more likely to have an explosion than dead yeast. If you haven't done so already, slowly cool it down to the proper range. Otherwise, it is likely to stay hot & make nasty.
Don't fret it. I did the exact same thing on this last batch. My chiller coils were touching my temp probe so when it was reading 75 degrees the actual temp (which I learned after pitching) was probably closer to 100 degrees.
7 hrs later I had active fermentation. I used US-05 also.