Paris Hilton has an obsessed fan who seems to be as loaded as he is angry, because he bought her an amazing classic Cadillac, and when she refused it, someone mysteriously trashed the whip.

The guy -- whose first name is Johnny -- delivered the Caddy to Paris' Bev Hills gated community onOscar Sunday. We're told Johnny got past the guard at the front gate by posing as a flower delivery guy, but when he rang Paris' door ... she called the cops.

The car sat on the street for two days, and on Tuesday someone bashed in all the windows. According to sources, Paris is convinced Johnny is the culprit because she wouldn't accept the gift, complete with flowers in the backseat.

Law enforcement sources say they've been on Johnny for a long time. He once flew a plane over the Hilton's Malibu compound with two signs, one of which read, "Can't Get Paris Whitney Hilton Out of My Mind." The other read, "Mr. & Mrs. Hilton, may I court your daughter Paris?"

Johnny also once sent Paris a really expensive wedding dress in the mail with a card that read, "Will you marry me?"

As for the Caddy, it's still sitting on the street because it's legally parked and registered to Johnny.

Paris was spotted on the street with the car on Tuesday, taking photos of it as "evidence."