This particular car has the Teves ABS, which was no longer used from 91(could be 92) on. I am not too familiar with how these work, but I recall a common failure point is the accumulator, which is the black canister looking thing on the top. What happens when that fails is that when you hit the brake pedal, you will be faced with a rock hard pedal, and the pedal will move down, and braking will increase as the pedal moves down. While this is happening, the brake and ABS lights will come on, while the pump is running (at the same time the pedal is going down). If you pump your brakes repeatedly, you may be able to replicate the symptoms.
These units are prohibitively expensive to service, and when they fail, many usually either grab junkyard units (crapshoot) or grab a non-ABS master cylinder/booster assembly and cut their losses