The high temperature in itself isn't the worst problem; the problem is
the higher the temperature, the less air that's in the water, which is why your fish are gasping at the top. They're essentially suffocating. Add air stones asap.
Rather than add ice cubes (which contain
chlorine and are just adding to the problem), the frozen water bottle is a good idea. I believe you can also buy fans to cool the water, but I don't know anything about them.
I imagine you are freaking out (I would be!), so hopefully these idea help. I'm so sorry you lost a fish from this.