Tehama County Assistant Sheriff Phil Johnston says investigators found the body of Kevin Janson Neal's wife hidden under the floor, and investigators believe this was the start of the rampage.
Authorities say Neal shot and killed four other people and wounded 10 others at different locations around the rural community of Rancho Tehama Reserve.
Officials said the shooter had been feuding with his neighbors, who were targeted Tuesday morning. The shooter was facing charges of assault, and one of the neighbors had placed a restraining order against him.
The shooting soon turned random, according to officials. At one point, the gunman tried to enter Tehama Elementary School, but quick thinking by teachers after hearing gunshots put the school on lockdown, and the shooter couldn't get in.
One student was shot and injured at an elementary school after shootings occurred at seven separate scenes near the town of Red Bluff. A second child and a female adult were shot in a truck, authorities said.
The gunman was killed after two officers engaged him, law enforcement officials said. The gunman had a semi-automatic rifle and two handguns.
At least 10 people were hospitalized after the shooting spree. Police said that students at Rancho Tehama Elementary School were among those transported to hospitals, but confirmed no children were among the dead.
The student shot is the little cousin of resident Gerardo Garcia, who works at his family's store in town. He said his cousin, Alejandro Hernandez, had two bullets removed and is expected to survive. "You hear about this happening all over the country. Once it happens to you, it seems unbelievable at first, but it happens here now," he said.
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About 100 students attend the school, according to an official.
On Tuesday, officials said the incident could have been so much worse if it wasn't for the quick thinking of staff at the elementary school.
The shooter rammed the fence and gate of school, entered the grounds with a semi-automatic rifle and fired multiple rounds.
It appears, officials said, the gunman couldn't access school rooms, so he gave up, re-entered his vehicle and took his killing spree to the streets.
One parent who was in a classroom locked down with 14 kindergartners described over the phone how the shooter was firing into the school. "There was gunshots going for a good 20 to 25 minutes. My window was hit with, like, a few shots, and the student injured was in my classroom. It was within seconds of me looking out the window to see if I can see the shooter, and he got nailed," said parent Coy Ferreira.
The Corning Elementary School District issued a statement, saying at least one student was shot during the lockdown, but the staff's "courageous and immediate response...prevented any further injury or violence."
The statement, in part, read: "The gunman shot out windows and through walls. In addition to injuries from broken glass, a student on campus was wounded by gunfire. We are informed that the student is in stable condition. The District has accounted for all of the students and staff present at the time of the incident. Parents have been notified. Counselors will be made available to meet with students and staff."
Law enforcement officials said the suspect had a history of neighborhood disputes and may have been released on bond for a previous incident.
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Authorites say the shooter had multiple runs in with the law - including a domestic violence dispute. He was facing prosecution for assault with a deadly weapon after stabbing one of his neighbors in January. Authorities believe a neighbor may have been his original target.
The shooter's mother also says her son was in trouble and tells the Associated Press that her son called her a few days before the killing and said "It's all over now." "I'm on a cliff and there's nowhere to go."
Police say the shooter did not have a license to carry a gun - yet he had three of them on him at the time of the shootings.
ABC News and the Associated Press contributed to this story.
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