give way traffic rule and indicating

I was waiting to turn into a side street accross the road. The car on the other side of the road, slowed down a little and indicated to pull into the same street (it was on his side of the road).
I assumed he was going to stop and give way to me, so proceeded to turn.
They suddenly changed their mind and sped up going straight ahead and hit me.
Am I at fault because I should have waited for them to start their turn before moving, or should they be at fault because the didn't follow through as indicated.

you are wrong. when making a left turn you must yield to oncoming traffic.