a lot of cars have audible wear indicators, they're just spring metal that touches the disc when the pads are worn down and these could be what you're hearing. however since you say the AVS is activating as well there is the possibility that the noise is because the friction area of the pad has gone completely. this means that brake will be doing less so the duty of slowing the car is spread amongst the other wheels raising the loads on the tyres, this can result in one or more of those becoming close to lock up, hence the ABS activating. heavily warped / worn discs can have the same effect.
whatever get the brakes looked at, not being able to go is inconvenient, not being able to stop can be far more serious.
EDIT: when you say the ABS is activating, do you mean you're getting a warning that it is or is it just the pedal that is vibrating? if it's just the pedal then it may actually be warped discs that you're feeling