On Maria Avenue just off Clayton Road and the ammo was in the back of a pick-up truck.
Experts from Travis Air Force Base in Fairfield arrived to check it out. The Walnut Creek bomb squad was there earlier on Thursday evening, but they didn't feel they were as qualified to deal with the situation as the people of Travis.
In the truck were four military-grade mortars. They ended up in the vehicle when the homeowner was helping a friend clear out her house. She brought them home thinking they were just empty shells.
"I just literally didn't cross my mind or occurred that these might be live. I just didn't. And then once I got to thinking about it, a little voice started with the, 'you know, you might want to have them double checked,' so I called. Immediately they said 'Don't get in your truck, don't open your truck, don't open the back, don't go in your truck for any reason, don't move it.' So I didn't," said Concord resident Theresa Musson.
Concord police immediately cordoned off the area and evacuated about a dozen homes.
After five hours, the experts from Travis determined the mortars were in fact empty.
They x-rayed each mortar, dismantled them, and hauled them away.
So there was a lot of inconvenience and a lot of resources for nothing, but the good news is everyone is safe and the worry is over.