He's done no wrong. He is just curious. And why wouldn't he be about such beautiful animals? Illegal where he is or not. He has the right to ask questions.
To date a rays venom alone has not been found to have killed anyone.
There is a story in the amazon of a fisherman who pulled a ray aboard and was stung in the chest. It is said that the barb penetrated in or close to his heart. Sadly he lost his life. Yet stingray venom alone has not yet been proven to take someones' life.
It is just VERY painful. My friend described it as being the "worst pain she has ever felt". Nausea, swelling, shooting pain up her arm and sweating. Fun right?
All the more incentive to be more careful when working around these creatures and to give them the respect that they deserve.
They are not intent on stinging. In fact it can take quite a bit of harassment before a ray resorts to that sort of defense. When it comes down to it they would rather flee.
In most cases in captivity, a sting comes from startling a ray.