Hannah Serfass was pronounced dead on Sunday (30 April) after falling on her head.

The 15-year-old equestrian was competing in the Fox Lea Farm Spring Concours I in Venice, when the horse she was riding suddenly "tripped" and suffered a "rotational fall," the US Equestrian Federation said in a statement.

According to NBC News, the Sarasota County Sheriff's Office said the teenager was about halfway through the course in the event when she tried the sixth jump.

"The horse landed the jump successfully and took two or three steps/gallops toward the next hurdle and for unknown reasons planted its left foot, which caused the horse to lean down significantly towards its left front hoof," authorities said.

Police said this then led the young rider to "topple" forward and fall off the horse.

"The horse then continued to fall in the same direction falling over and onto the rider's head on the ground," the sheriff's office added.

Officials said emergency services responded quickly and transported the injured girl to a local hospital, where she was later pronounced dead.

'A very talented up-and-coming young rider'

Hannah Serfass was an up-and-coming rider and was known for her passion and love for horses.

The US Equestrian Federation said on Monday: "It is with our deepest sympathy the United States Equestrian Federation (USEF) announces that Hannah Serfass suffered a fatal accident yesterday, 30 April, while competing at the Fox Lea Farm Spring Concours I in Venice, Fla.

"Hannah, 15, was riding Quaxx 2, a 12-year-old Holsteiner gelding, in an equitation class when the horse tripped and suffered a rotational fall. The fall was unrelated to a jumping effort.

"The EMT responded immediately, and Hannah was transported to Sarasota Memorial where she was pronounced dead. The horse was uninjured in the accident.

"Hannah from Webster, Fla., was a very talented up-and-coming young rider who trained with Robin Swinderman.

"She was known for her passion for horses, her natural ability, and her work ethic."

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In a Facebook post on Monday, Fox Lea Farm shared their "sincere condolences" to the rider's family and said they were "heartbroken" by the "tragedy".

The post read: "Fox Lea Farm had a tragedy occur today.

"Out of respect to the family, no information will be shared at this time.

"We send our sincere condolences to the family, trainer, friends, & the whole equestrian community.

"We are all heartbroken."