As investigators piece together the moments leading up to the horrific shooting rampage in Rancho Tehama, Calif., they realized their fears were confirmed when they found the dead body of the shooter’s wife. 

Before the deadly attack, which killed four adults and injured at least nine others — including children — Kevin Janson Neal reportedly shot his wife and buried her beneath the floorboards of their home, reported the Los Angeles Times.

After the Tuesday attack, police attempted to contact the shooter’s wife, who has not yet been identified. When they were unsuccessful in their attempts, they assumed the worst.

Detectives conducted a search of the couple’s home on Tuesday evening, which is when they found her body, which had been shot several times.

"We believe that's what probably started this whole event," Tehama County Asst. Sheriff Phil Johnston told reporters Wednesday.

The death of Neal's wife brings the total number of people shot and killed in the town to five. Neal was fatally shot by officers pursuing him down the road from the school where he opened fire.

Police believe Neal shot his wife on Monday and hid her body, then went out into his community the next day and opened fire. One of the people he killed was his female neighbor, who he’s had issues with in the past.

Down the road from his home, he also killed two men, then stole a Ford F-150 pickup truck, according to Johnston. He drove north, firing a semiautomatic rifle at random from the vehicle.

While driving down the road, Neal fired eight rounds into a Ford F-250 driven by a mother with her son in the car. The two were headed to Rancho Tehama Elementary School when Neal fired into the car. The boy suffered non-life-threatening wounds, but the mother was seriously injured, Johnston said. The mother, who had a concealed carry permit, pulled out her own handgun but could not fire it.

By the time Neal arrived at the elementary school, authorities said, teachers had already placed students and staff on lockdown.

Determined to get onto the property, Neal barreled the stolen truck through the school's front gates and steered into the quad. He stepped out and fired randomly at the rooms around him.

One bullet pierced a wall and hit a boy, who is expected to survive. The boy, Johnston said, was the only student shot at the school.