The shooting occurred at Rancho Tehama Elementary, a small public school of 100 students located in northern California.
A second child also was reported to have been shot in the right leg, according to emergency dispatch reports.
A six year-old child with two gunshot wounds was reportedly transported by helicopter to a hospital.
The school is in the Rancho Tehama Reserve, about 130 miles north of Sacramento.
Jose Garcia, who owns the La Fortuna Market, about a half-mile from the school, said he heard "a lot of shooting" near the school shortly after 8 a.m.
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Unruh said her son, now a college sophomore, didn't report the incident to police at the time because of "embarrassment and fear". Her son is represented by Mitchell Garabedian, an attorney best known for representing clergy sex abuse victims.
"He said he saw bullets hit the truck in front of him, so he made his children get down and put his truck in reverse".
It's not clear if the shooter is included among the dead Tuesday.
He told Action News Now that there were at least seven crime scenes related to the incident.
Brian Flint told the Record Searchlight newspaper in the city of Redding that his neighbour, whom he knows only as Kevin, was the gunman and that his roommate was among the victims. Mercy Medical Center in Redding received three patients, including one who also was transferred elsewhere, said Harter, whose company, Dignity Health, runs both hospitals.
"The insane thing is that the neighbour has been shooting a lot of bullets lately, hundreds of rounds, large magazines", Mr Flint said.
"The insane thing is that the neighbour has been shooting a lot of bullets lately, hundreds of rounds, large magazines", Mr Flint said. Police recovered a semi-automatic rifle and two handguns they believed were used by the shooter. "This guy has been insane, and he's been threatening us and everything".