Juvenile starling

Hi guys. So I was just putting some water out for the birds and one of the starlings that was hiding in the tree(we have a couple of sparrowhawks that have them constantly jumping at the minhte) just fell out, he was gasping, so I came to get some thing for my hands to pick him up and went to pick him up and he just stopped breathing. He landed on concrete, however he was bleeding in his mouth. But he literally fell out the tree so assuming he was already in the dying phase. However, could he have been choking or something? We clean the feeders, water dishes, I soften the mealworm up before putting it out. I'm just in shock and not entirely sure what happened. I've got him in a box in the trailer in the garden because I can't bring myself to just throw him out. I'm gutted. I love our starlings so much. I'm not sure if it's the one that has been in the garden a while however because we have had one that's constantly coughing but when ever I got too close he would fly. I just feel so sad now that I couldn't do anything. But I'm just wondering if anyone has any idea what could have happened?

Thank you in advance. 

Sarah