(CNN) -- The ground just swallowed him up.



A Florida man fell into a sinkhole that opened suddenly beneath the bedroom of his suburban Tampa home, calling out to his brother for help as he fell, a fire department spokeswoman said Friday.



"I heard a loud crash, like a car coming through the house," the man's brother, Jeremy Bush, told CNN affiliate WFTS. "I heard my brother screaming and I ran back there and tried going inside his room, but my old lady turned the light on and all I seen was this big hole, a real big hole, and all I saw was his mattress."



Bush frantically tried to rescue his brother, Jeff Bush, standing in the hole and digging at the rubble with a shovel until police arrived and pulled him out, saying the floor was still collapsing.



"I thought I heard him holler for me to help him," the man tearfully told WFTS.



Jeremy Bush and four other people, including a 2-year-old child, escaped from the blue, one story 1970s-era home in Brandon, Florida, a Tampa suburb.



The man was presumed dead after monitoring equipment lowered by engineers detected no signs of life, said Jessica Damico, the Hillsborough County Fire Department spokeswoman.



But rescuers can't go into the hole to check -- it's too dangerous. Authorities say they worry the hole is still spreading and the house could collapse at any time.



Authorities evacuated nearby homes as well -- in case the hole keeps growing, Damico said.



The sinkhole is naturally occurring and appears to be about 100 feet (30 meters) across, based on estimates made by engineers using radar, and it may be as deep as 50 feet, authorities say. It's not visible except inside the home.



About 40 police and firefighters were at the scene Friday morning, waiting for engineers with more sophisticated equipment to examine the sinkhole, Damico said.



Family members were also on hand, waiting out what they fear will be a devastating day.



"I know in my heart he's dead," Jeremy Bush said. "But I just want to be here for him, because I love him, he was my brother, man."



Sinkholes are common in Florida, according to the Florida Department of Environmental Protection. The state lies on bedrock made of limestone or other carbonate rock that can be eaten away by acidic groundwater, forming voids that collapse when the rock can no longer support the weight of what's above it.