In what park officials called a "billion to one" tragedy, two giraffes were killed by lightning at a Florida safari park.

Lion Country Safari in Loxahatchee, Florida, said Tuesday that recent medical reports confirmed that the giraffes died instantly last month when they were struck by lightning.

"It's like a billion-to-one chance this happened to us and our poor giraffes, but we are looking at anything we can to improve upon" safety for the animals, safari spokeswoman Haley Passeser told NBC News.

The park said the giraffes, named Lily and Jioni, were in a pasture when the lightning hit them but that they had access to multiple shelters in their multi-acre habitat.

No park officials saw the lightning strike, so it wasn't clear whether one or two bolts killed the animals, Passeser told NBC News.

"It was absolutely heart-wrenching," the zoo's wildlife director Brian Dowling told WPEC-TV. "This was just an act of Mother Nature that we couldn't stop; we couldn't alter how that came about."

The park, which bills itself as a "drive-through safari" and "cageless zoo," had 20 giraffes before the deaths, NBC reported.

Follow USA TODAY's Ryan Miller on Twitter @RyanW_Miller