Hello and welcome to JustAnswer!
There is some sort of problem that the ABS module has picked up on. The first things to do would be to check fuses, and check the brake fluid level. If there are any leaks in the system the lights will come on and set a failure code for "foundation brake" because there is a pressure drop in the system. Also check out the wiring to the front speed sensors at the wheels, and the rear speed sensor on top of the rear differential. if this is all ok, the next step would be to have the failure codes read with an ABS module capable scan tool or special ABS code reader. If the light is on there are codes stored to tell you what direction to go to diagnose it. There are near 40 different codes that can set.
Keep in mind that when the ABS light is on the system will be disabled, so until you get it fixed you won't have any ABS. If you stop fast and the brakes lock they will stay locked just like if you didn't have ABS.
I would definitely recheck the fluid level, go over all of the lines and fittings and make sure there aren't any leaks. Any leak can cause this.
Hopefully the wiring is ok. Sometimes it can get hit with road debris, and I've also seen heat from sticking calipers take sensors out too. Look for any signs of damage all the way down to the sensor.