(NewsNation) — A seven-year-old girl has died and her nine-year-old brother is hospitalized after a hole the children were digging in the sand collapsed on top of them.

The children, identified as Sloan and Maddox Mattingly, were playing on a beach in Lauderdale-by-the-Sea, Florida and, according to onlookers, were digging a hole in the sand before it collapsed on top of them.

The Mattingly family was vacationing from Indiana and it’s not clear if any adults were helping the children dig the hole.

Emergency crews responded around 3 p.m. Tuesday and found Maddox buried in sand up to his chest with his sister completely buried beneath him. Witness video showed bystanders also helping try to dig the children out.

First responders had to use boards to shore up the sides of the hole, which officials estimated to be five to six feet deep, to prevent it from collapsing further.

Rescue experts suggested the girl’s death could have been prevented if lifeguards had been on duty at the beach because they could have warned the family against digging holes deeper than two feet due to the risk of collapse and stopped the children before the sand caved in.

Sloan Mattingly was pronounced dead at the hospital after being extricated and Maddox Mattingly is hospitalized in stable condition.