Hope he acclimates quickly!
Another member posted not to long ago with the same issue. The fish is doing fine now I believe.
Dim the lights and avoid startling.
It could have been because of the temperature but acclimation problems are usually the result of osmotic shock due differences in TDS. Fish are often raised in hard water with high TDS and your water may have very low TDS. Adding say .. one tablespoon aquarium salt per 5 gallons would have increased TDS close to 1,000 ppm which is a good level for this.
I don't know but it was quite cold. He is recovering well now. Turned on the lights to take a quick picture of him. This is how he is now. Recovering slowly but strong.