I Moved My Neighbor's "Reserved" Parking Cones

My apartment complex has unassigned parking. My neighbor Greg has been placing traffic cones in "his" spot every morning for a year. There's no reserved parking in our lease. One morning, the lot was full and I moved his cones and parked there. Greg came to my door at 7am demanding I move my car. I said there's no assigned spots. He said "everyone knows that's my spot, I've lived here longer." I told him to talk to the leasing office if he wants a reserved spot. He left a passive-aggressive note on my windshield. The leasing office confirmed: no assigned parking, no cones allowed. Greg has now started parking his second car (which he barely uses) in the spot to "claim" it. I think he's being unreasonable. He thinks I started a parking war.