Windscreen wiper bracket Fires against disk, when buying used cars, who is liable?

Hello, today something very stupid happened to me. I looked at a car, when opening the bonnet, (the owner just changed the windscreen wipers, which I had not paid attention to at all), bangs the left wiper holder against the windscreen, there were several approx. 15cm long cracks and a big… no matter what the compelette windshield must be renewed. At the time of the damage, the car was melted on the owner, he is still. Then had The owner called the police, she said I had to be careful if I opened the hood, that nothing happened. The owner stand next to it. Now I should pay for the damage. If the owner had at this time, the wipers did not weave it, it would never have happened. And if I unlocked the hood, and wanted to open the hood, and the owner stands 1 meter next to it, he can carefully lower the wiper, don’t you think? On the change of wipes I have at all I did not pay attention, I once ran around the car, paid attention to the paint etc… Now I should pay all the numbers? That can’t be!!! What do you think, which insurance must pay for this damage???