Braking Under Heavy Snow

In the recent winter break out I noticed a puzzling thing about my
Yaris' brakes that I forgot to mention. It only came up to me today
after reading an article about Prius' brakes problem in USA.

I went out for a spin (to Tesco's )
in a really bad weather condition (snow, mud, -°C temperatures etc.) as
I love to drive in snow. As I approached a crossing with red light I
started to brake gently. I know ABS prevents the wheels from blocking
on slippery surface, but as I started to push harder on the pedal to
slow the car down a bit harder a very strange thing started to happen.

As
I've never driven an ABS equipped car before I'm wondering if it's
normal. Mainly, the pedal backed off my foot a bit, lost it's braking
feeling completely(very soft, loose with no pressure under it) and
started to rattle. It was a quite loud, sharp, numb plastic-y noise. As
if you were rubbing with force with something over a plastic gear (like
a pullback toy cars you play with and you pull them too much). You
could hear some mechanism being overdriven, overrun or something not
really right. It's hard to describe.

I noticed that at this
moment the wheel most probably started to slide over the surface as I
were loosing control over the car and that was what caused the ABS to
go bonkers.
I let the pressure off the pedal, and started to push on
it back again, but a bit more gentle. The braking feeling came back
with proper braking until you pushed it in again. It happened at only
icy road, never again.

Anyone knows if I should be worried about that?