The Contra Costa County Sheriff's Office received reports of shots fired near the intersection of Marina Road and Inlet Drive in Bay Point around 1:55 p.m., sheriff's spokesman Jimmy Lee said.
Deputies arrived at the scene and located the shooting victim, who was suffering from at least one gunshot wound. Lee said he did not have an update on the man's condition.
As of 2:45 p.m., deputies were still searching for the shooter or shooters.
At about 3:15 p.m., the sheriff's office was putting out automated emergency calls advising all people in the shoreline areas of Bay Point to shelter in place.
The message advised people to go inside and close all windows and doors; stay off the phone unless there is a medical emergency; and remain indoors for the next three hours.
Multiple schools in the area have gone into a self-imposed lockdown as the search is carried out, including Riverview Middle School in Bay Point and Shore Acres Elementary School in Pittsburg, Lee said.