The 3-year-old son of Explosive Red won the Affirmed Handicap (gr. III) at Hollywood Park in June and was also third in the Swaps Breeders' Cup Stakes (gr. II) in his last start on July 10.
"We're just crushed," trainer Vladimir Cerin said. "He was special; it was like having a gelding, not a colt in the barn."
Boomzeeboom, who raced for the partnership of John Karubian, Alan Landsburg and Larry Postaer, won three of 10 starts for $190,096. He was being prepared for a start in the Aug. 8 Haskell Invitiational Handicap (gr. I) at Monmouth Park.