A crew was filming the Discovery Channel TV show "MythBusters" at the Alameda County bomb range at around 4:15 p.m., sheriff's Sgt. J.D. Nelson said. They were doing an experiment using a cannon they had built about two years ago and which they have used at least three times before, Nelson said.
In this particular experiment, the projectile was intended to go through several barrels of water and a cinder block wall before striking the hills of the bomb range, Nelson said.
However, the cannonball missed its target.
It missed the water, which was intended to slow the projectile's progress, went through the cinderblock wall and struck the hill.
"It did not bury itself in the hill as you might think it would have," Nelson said.
Instead, it careened off the hill and into a neighborhood in Dublin, Nelson said.
The cannonball passed completely through a house on Cassata Place, creating a softball-sized hole, and continued down the street before it landed in a parked car, Nelson said.
Three people were at home at the time, including at least one child, but no one was injured, he said.
Nelson said the TV crew responded by sending a senior producer to the home and to the home of the car owner. The producer arranged to meet with their insurance carriers, Nelson said.
"They (the 'MythBusters' crew) are insured for these kinds of things," he said.
Nelson said the television show has used the county's bomb range more than 50 times for experiments and filming.
"We never even had any kind of an incident let alone anything this terrible," Nelson said.
Pratima Dsouza, who lives next door to the house that was hit, said she heard a loud noise and later saw police responding to her neighbor's home but thought there had been some sort of accident inside the house.
It wasn't until she saw it on the news that she learned what had happened.
"Nobody came to our door and told us there was a cannonball that went through our neighbor's house," Dsouza said.
She said the bomb range is some distance from her neighborhood.
"We can hear the sounds but we've never had an experience like that before," she said. She said a family lives in the home that was struck.
Another resident, Mark Hawthorne, said the cannonball bounced off of Cassata Place, leaving a dent in the concrete before crashing into his neighbor's house.
He said neighborhood kids -- including his own -- often play outside in the cul-de-sac around where the cannonball landed.
"It's a little scary," said Hawthorne, who has watched MythBusters on occasion. "It's easy to laugh at after it's done and no one's hurt."