(AP) — Kentucky Derby winner Medina Spirit has collapsed and died after a workout at Santa Anita.

The 3-year-old colt trained by Bob Baffert had just completed five furlongs in his second workout since finishing second in the Breeders’ Cup Classic a month ago at Del Mar.

Baffert confirmed the colt’s death and attributed it to a heart attack.

Medina Spirit will undergo a full necropsy, which is required by the California Horse Racing Board.

In his last race, Medina Spirit finished second in the $6 million Breeders’ Cup Classic at Del Mar a month ago.