Bad little children with noisy toys

We live in this nice building, but our balcony looks over the alley way. Therefore, any noise in the alley travels up and reverberates off of the building right behind us and is amplified.
Well, our neighbors thought it would be a good idea to buy their spoiled children these little noisy motor scooters, and all day and all night they race up and down the alley, honking their horns and yelling.
Well, I get why they are playing in the alley rather than in the street. They can't possibly realize how loud it is for us who live in these units that face the alley. If they do realize it, I doubt they care. Marco has asked them several times to keep it down, and apparently the other neighbors have asked them as well.
So, on Friday night after they had been doing it for hours, they began to taunt an old man who asked them to knock it off.
Then the yelling began.
"Get out of here you little assholes", "No, we don't have to mind you". On and on like that until the old man started yelling "I will kill you" and he threw a potted plant at them and then some little pottery dish which shattered all over the cement.
Then they came back with their parents and acted so sweet and innocent and played the victim.
Yesterday they came back in full swing. Zipping up and down and making sure to yell and honk right under the old man's window.
Which was incidentally right under my window too.
There are now eggs all over the cement. I hope he nailed them.