Weird sound when rolling backwards.

I've had my truck for about a month now. I was playin around with different features and what not while I was parked on a pretty steep hill facing up. While it was running I put the truck in drive and let my foot off the break. I rolled back about 3 feet and the truck made a noise that I could feel in the pedals. Similar to the ABS noise. And I remember a light flashing. Anyone shed some light for me?

 

Telling us what light could be helpful.............

 

hill start assist

 

I thought of that. But I couldn't remember what it looked like, so I left it at that. This happened a little over a week ago and I was just thinking about it while I'm in my hotel room out of town for work. Sorry.........

 

So it's not necessarily a bad thing?.. I just wanted to make sure nothing was wrong. I drove a rental car a few weeks ago in San Francisco that had a "hill assist" feature, and it would hold the car in place momentarily, to allow enough time to press the gass without rolling backwards. Is this the same? I attempted it twice but the truck still rolled back..

 

I've got it figured out guys. I guess searching a little harder on my part would have been a good idea... Thank you for the input.