The blast at about around 10:20 a.m. Sunday forced the evacuation of surrounding homes in a cul-de-sac in Vacaville, which is located between San Francisco and Sacramento.
The unidentified man was airlifted to the University of California, Davis Medical Center. The extent of his injuries was unknown. It also wasn't clear whether the attack was random or the man was targeted.
Residents within a roughly half-mile radius of the explosion were advised not to approach any suspicious packages. Vacaville city spokesman Mark Mazzaferro says a search of the cul-de-sac didn't turn up any other explosive devices.