The Riverside County sheriff told The (Riverside) Press-Enterprise six juveniles were arrested soon after the alleged March 10 attack at Victoriano Park in Moreno Valley.
The seventh suspect, Michael Sykes, 19, termed a gang member, may have fled to Los Angeles, deputies said.
Sheriff's Investigator Matt Diaz would give no further details on the case, which was not revealed until Sunday, to avoid jeopardizing the investigation.
The assault was gang-related, said Capt. John Anderson, chief of the Moreno Valley station. He said the park and surrounding neighborhoods are not known as high-crime areas.
"As a father -- even as a police officer -- there are crimes that shock us," Anderson said. "This is one of them."