Constant bugging/teasing with younger sibling

I have 3 kids: a 5yo boy, a 3yo girl, and a 2mo boy. Sometimes the 5yo and 3yo play great and are so cute together, but much of the time I’ve noticed this dynamic that drives me up a wall.

Basically, the 5yo is constantly bugging 3yo with either teasing or getting into her personal space unnecessarily. 3yo will then scream and cry for us, which 5yo thinks is amusing and will then want to do more of the annoying behavior. This happens when one or both parents are around, not when they are alone (they share a room)

Example 1: we are on a walk. 5yo picks up a rock and shows me, I tell him it’s cool. 5yo walks up to 3yo and starts teasing that he has a cool rock and she doesn’t. 3yo cries and plops onto the sidewalk

Example 2: we are playing in the living room. 5yo picks up a toy car and starts zooming it in 3yo face. 3yo screams and tells us she’s scared and that he’s bugging her

This has been going on for 6+ months so I don’t think it’s related to the new baby. Both kids are in full time preschool

Any stories or ideas on how to improve?! So far I’ve mostly been talking to 5yo about how he wouldn’t want to be treated that way. My mom taught 3yo to pretend she’s in a bubble and that nothing can reach her, which she liked for a bit, but now 5yo pretends to pop the bubble and 3yo gets very riled up about that 🤪