Generation 2 brake problem. HELP!

Okay, I'm new here, though I've read a lot of articles on the forums here. I'm trying to fix my 2007 prius, it's had quite a few little problems which I've been working through, but here's the latest which has me parking the car and not driving it at all until I figure it out.
I was test driving making sure I had gotten one issue dealt with, and while going 55 mph on my curvy state highway, a deer walked right into the road. I applied the brakes and the rear brakes locked up and the car began to fish-tail. It was a sunny day, about 50 degrees Fahrenheit, the road was dry and was paved last year. There were no bumps and no gravel in the road. I let off and hit the brakes again, but lighter, they locked up again. I managed to keep control of the car, but no longer had any trust in the brakes. I then tried different ways of hitting the brakes, and even as slow as 10 mph, they would lock up. After doing research I found a lot of people talking about various problems with the gen 2 prius braking system, but none with the same issue. Either the brakes weren't doing anything, or the rear brakes were locking up after hitting bumps or on wet days.

That being said, the brake light, circle with exclamation mark, ABS, VSC and tpms lights are on.
What I would like to know is how can I fix this, where do I start? There is no nearby Toyota dealer, I think the closest one is about 2 hours away, and I for one am not going to drive there, neither do I have a way to get it there.

 

Here's a video I took. That engine tick is one of the problems I've been trying to fix. In the mean while I've not been driving it except for test driving.