RICHMOND -- Authorities scrambled Thursday to keep up with an apparent outbreak of gang violence that has resulted in six shootings over a 21-hour period.

The violent outbreak soared within a one-hour period Wednesday when three of the shootings took place.

At 12:07 p.m., Richmond police received a report of gunshots at Roosevelt Avenue and Harbour Way, Sgt. Dave Harris said. Police found gun casings and a shot-off car bumper. Two blocks away, police located a car with several bullet holes, but found no victims or suspects, Harris said.

About 40 minutes later, reports of gunshots brought police back to the same Roosevelt Avenue and Harbour Way intersection where they found two people suffering from bullet wounds, Harris said.

One man in his 40s was shot once in the head and another man in his 20s was shot twice in the stomach, according to Harris. Both men were transported to John Muir Medical Center.

Harris said that at 12:41 p.m. police responded to reports of gunshots at Kelsey Street and Gertrude Avenue. Although police did not locate any victims at the intersection, they were alerted that the Contra Costa Sheriff's Office had responded to a shooting just blocks away, at Third Street and Silver Avenue.

Two people were found with bullet wounds and were taken to Doctors Medical Center in San Pablo, Harris said. The extent of their injuries was not available.

About nine hours later, at 9:30 p.m., officers heard numerous shots fired in the 200 block of South Fifth Street, Harris said. Harris said that officers found bullet casings and that the victim of the shooting drove himself to Keiser Hospital. He suffered three bullet wounds to his ankle and lower leg.

Authorities are investigating the shootings and no arrests have been made, Harris said.