Neal, identified as the gunman who killed four people in a string of shootings Tuesday, shot and killed his wife the previous night and concealed her body under a floor in his home, Tehama County Assistant Sheriff Phil Johnston said.
The discovery of her body brought the death toll to five.
"We believe that's probably what started this whole event," Johnston said of the wife's shooting.
Neal had been out of bail on an assault with a deadly weapon charge from January, officials said.
Before police shot him dead, Neal injured at least 10 others in a string of shootings that spanned at least seven sites