Really?

Question for some mommy friends...here's the situation.

Today I took Kyle to a public play area at a local church, with play tubes, slides, etc. There were only a few other children there, so it wasn't busy at all. Well, this little boy, around three/four years old, is running around like a mad man, and his mom is repeatedly yelling his name. Over, and over, and over, telling him to slow down, come here, whatever. Anyhow, Kyle was standing next to him at one point, smiling...the other boy looks at me, then him, then aggressively shoves Kyle down with both hands--while grinning. I politely say, "uh oh, no, let's play nice, he's a little baby". The kid looks at me again, then him, and shoves him down...again. Kyle begins to cry. I look at the boy, pick Kyle up, and as soon as he's on his feet, this kid shoves him down AGAIN! Oh and that's not all...I grab Kyle and walk him away from this kid, and he comes up from behind and shoves Kyle down from BEHIND! Oh heck nooo....not cool Shamrock...or whatever wierd name your parent gave you.

At this point I'm really ticked off. I look around and his mother is over running her mouth to another mom. I just let it go, because obviously this kid has no rules or boundaries, as I saw when the mom had to chase and yell at him for thirty minutes to get him to leave. I know he's a toddler, but purposely shoving a baby down multiple times? And I don't mean a little shove, I mean this kid used both arms, as hard as he could! Kyle slid back this kid shoved him so hard!

Anyhow, what do you do in that situation? Get onto the child? Move your child away? Go let the parent know?  Trip him? My teacher instincts make me want to redirect the child's behavior and go "address" the mom, but this parenthood thing is new. Other kids think Kyle is much older than he really is, because he looks more like a two year old than 13 months. But still, this kid was one shove short of a thumb in the eye. Any suggestions?

Possibly obsessive helicopter mom,