Four people died and 15 others were injured in a shooting incident late Sunday at the annual Gilroy Garlic Festival in Northern California, Gilroy police confirmed at a press conference.

Armed police on the scene of a shooting during the Gilroy Garlic Festival along Miller Avenue near Gilroy High School. [Photo: San Francisco Chronicle/Polaris via VCG/Cody Glenn]

Gilroy Police Department Chief Scot Smithee told reporters that the suspected gunman used a tool to "cut through the fence to gain access to the security fence line" and entered the grounds of the festival.

He said some witnesses saw the gunman seemed to shoot randomly into the crowd with "a rifle," sending the revelers running in panic to seek safety.

Smithee said he had no specific information about the shooter at the moment, but confirmed the gunman was "down" after being shot in less than a minute after police officers engaged the suspect.

"I don't have any information on the suspect yet ... That will take some time before we identify them," he said.

He said some witnesses reported there might be a second suspect, but he did not have "specifics on that, other than people reported a subject leaving the area that they thought was associated with this person."

He said the police and investigators are engaged in an active probe into the shooting, which will probably continue throughout the night.

The Gilroy police chief called the shooting incident a "nightmare" for the Gilroy community.

The shooting took place Sunday evening at Christmas Hill Park in Gilroy city, about 80 miles (about 129 km) southeast of San Francisco. Some witnesses said they heard a gunshot was fired near one of the musical acts.

Gilroy Mayor Roland Velasco also said at the press conference that he hoped the public would assist authorities in conducting the investigation.

"I would ask for the thoughts and prayers of the community as our Gilroy police officers continue to investigate this tragic and senseless crime," he said.

"We are again continuing the investigation, and we plan on being out here all night," said the mayor.

Gilroy city said in a statement a search is still underway for the possible second suspect as reported by the witnesses.

California Governor Gavin Newsom has expressed his support for the Gilroy residents, calling the shooting "horrific."

"This is nothing short of horrific. Tonight, CA (California) stands with the Gilroy community. My office is monitoring the situation closely. Grateful for the law enforcement's efforts and their continued work as this situation develops," he tweeted.

The Gilroy Garlic Festival, which started in 1979, is now known across the globe as the world's greatest summer food fair, featuring three full days of garlicky food, live entertainment, and family fun.

Sunday was the last day of the annual three-day festival, which often attracts tens of thousands of garlic lovers.