The wife of the gunman who went on a shooting spree in Northern California was found dead Wednesday, her body hidden under a floor inside their home — bringing the madman’s death toll to five, police said.

Investigators believe Kevin Janson Neal, 43, began his rampage in rural Rancho Tehama Reserve on Tuesday morning by killing his wife, said Tehama County Assistant Sheriff Phil Johnston.

“[We believe he] cut a hole in the floor and literally put her body in the hole,” Johnston said, adding that investigators believe she was killed Monday.

Neal — who was out on bail on charges of stabbing a neighbor, a woman who was killed Tuesday — went on the rampage a day after he was the subject of a domestic violence call, officials said. No details were released about the call.

According to his mother, Neal was increasingly frustrated with an ongoing dispute with his neighbors, who he claimed were running a meth lab with fumes that were harming his nine dogs.

His neighbors have complained about how Neal fired hundreds of rounds from his house.

In addition to his wife, Neal killed four people and wounded 10, including a 6-year-old boy, at seven locations before police rammed a stolen vehicle he was driving and shot him dead.

Neal’s mother, who only gave her first name, Annie, said he called her to apologize a day before his attack — saying he was at his wits’ end.

“‘Mom, it’s all over now,’” Annie said he told her. “‘I have done everything I could do and I am fighting against everyone who lives in this area.’”

The following day, he donned a ballistic vest, grabbed a semi-automatic rifle and two handguns and set off on his 45-minute rampage.

He killed two neighbors, stole their truck and drove around, randomly picking off targets en route to the Rancho Tehama Elementary School, where staffers heard gunfire and ordered a lockdown.

“The quick action of those school officials, there is no doubt in my mind, saved countless lives,” Johnston said. “He did shoot at a number of classrooms which resulted in the injury of at least one or two students that I’m aware of.”

Moments later, a patrol car rammed Neal’s vehicle before officers opened fire and killed him.

One of those injured was the 6-year-old boy, who was hit inside the school, the Sacramento Bee reported. A cousin identified him as Alejandro Hernandez.

Arlene Monroy, 17, told the Bee that she had been told Alejandro was shot in the chest and leg, but was expected to make a full recovery.

Johnston said Neal’s motive appeared to be to exact revenge on his neighbors.

His mother said Neal — a recently married pot farmer — sounded increasingly despondent over his toxic relationship with his neighbors.

One of those killed Tuesday was the woman whom Neal was accused of assaulting in January, the Bee reported.

Annie said her son told her that the woman, who was threatening him with a steak knife, was slightly cut when he pulled it out of her hand.

The mother, who lives in Raleigh, North Carolina, where she raised Neal, said she posted his $160,000 bail and spent $10,000 on a lawyer.

Johnston said he believed Neal was slapped with a restraining order after the January arrest that would have prevented him from owning firearms, at least temporarily.

In April, the District Attorney’s Office charged him with assaulting a second person, also in late January, according to Tehama County court records.

Tehama DA Gregg Cohen told the Bee that his office was prosecuting Neal on charges related to a stabbing and assault with a deadly weapon involving two of his neighbors.

Neal’s sister, Sheridan Orr, said she had not talked to him in months, but that he had struggled with mental illness and at times had a violent temper. She said she believed he was addicted to drugs.

“We’re stunned and we’re appalled that this is a person who has no business with firearms whatsoever,” Orr said. “Our deep, deep sympathy for the victims and it sounds trite but our hearts are breaking for them.”

With Post wires