04 Hyundai Elantra all four brakes are locked up?

I have a Hyundai Elantra GLS 2003 with "anti-lock brakes." I rear ended a car on the highway last night and on recolecting as carefully as I can, I braked, and I believe I braked in time. The car didn't stop. I don't believe it even slowed down appreciably. A friend of mine said that the "anti-lock" mechanism RELEASES the brake when it senses a skid. But what logic there is in not braking immediately after the release (in an automatic pumping motion) escapes me entirely and I braked immediately and I braked hard. I am considering taking Hyundai to court. I'd be grateful for any information or incidents others have experienced.