Paint got on a neighbors car, who is responsible to pay for damages?

My son is 12, lately a boy I will call James has been coming by to ride bikes and hang out in the front yard. I had never met James mom, the boys just had an outside friendship of about 2 weeks. A couple days ago the boys were riding bikes and James found a can of spray paint in the gutter, he took one of our garden tools and punctured it spraying a mist of paint ALL over our neighbors car. James told my son to hide the paint and not tell adults. My son immediately got me and I went with the boys to apologize to the neighbor and tell him what happened. I think its fair for our family and James family to split the repair cost. My son didnt even touch the spray paint ( this is all on video as the neighbor has high quality security footage we all watched) but I will pay half. When I went to James house to let the mom know what happened, she said she wont pay because it happened near my house, so I should be responsible. I am in no way responsible for her kid, until I delivered the news of the spray paint I had never even met her. This kid just comes by to bike with my son, I have zero obligation to watch him. Opinions? via /r/Parenting https://ift.tt/2MTSZ5c