my cat treed a chipmunk

I saw the cat outside looking at something intently in the grass. I went over, thinking it had found a snake or large insect. It was a chipmunk. Behaving odd- it was leaping up and down short hops with its back arched, not moving away from the cat. Once it jumped up against the cat's side, who just turned his head to look at it, confused? I thought for sure the chipmunk had a severe injury, nerve or brain damage. Then it suddenly bolted up a nearby tree. My cat tried to follow but the chipmunk went pretty high.

It was up there for hours- I kept going out to look. I didn't see when it come down. I don't know if the cat was still waiting there, or if the chipmunk escaped and made it back to its hole.

It sure was acting strange, so I kind of hoped if it was seriously injured, the cat ended its life quickly.