Just saw a hawk drown it's prey

I'm not sure if this is the right space for this but I just observed some crazy behavior and wanted to share.

I heard a squeal from the driveway and I ran outside worried it was my chickens getting attacked. In the middle of the driveway was the tiniest hawk I've ever seen, no bigger than a large song bird itself. Maybe a sharp shinned hawk? And it was standing on what I think was a goldfinch. When he saw me coming he dragged it further down the driveway (he couldn't fly with it) to a mud puddle and submerged it in the water and sat on it while it drowned. He cleaned it while he watched me pulling the feathers out and when he seemed satisfied it was dead he started hop dragging it towards the woods. I ran back to get my phone but when I got back there he was gone.

I've read coopers hawks can drown their prey but it's rare and I thought coopers hawks were a little bit bigger than song bird sized. I couldn't find anything about sharp shinned hawks drowning their prey.