A central Florida woman who fatally shot her son then killed herself at a shooting range wrote in suicide notes to her boyfriend that she was trying to save her son.

"I'm so sorry," Marie Moore wrote several times. "I had to send my son to heaven and myself to Hell."

She signed two of the notes "Failed Queen."

Authorities said Wednesday they still had no motive for the murder-suicide that shocked fellow customers and employees at the Shoot Straight range in Casselberry, about 10 miles north of Orlando, on Sunday.

"We have no clue. I don't even want to begin to speculate," said Deputy Chief Bill McNeil of the Casselberry Police Department.

Son shot in back of head

The gun range's security video shows 20-year-old Mitchell Moore taking aim at a target in a booth when his mother, 44, walks up behind him and points a gun at the back of his head. In the next frame, the son is seen falling to the ground and a nearby patron appears to alert others as he points to the unseen carnage.

The gun used was rented at the range.

According to a police report, earlier footage from the surveillance video shows the mother and son taking turns shooting and talking with other customers in the adjacent lane. "They seem to be getting along fine," one of the responding officers said.

The son died at the scene. Marie Moore was still alive when officers arrived at the range but later died at a hospital.

Woman reportedly had mental illness

Mitchell's father, Charles Moore, told police that Marie Moore had a history of mental illness and had previously attempted suicide and been involuntarily committed to a mental hospital in 2002 under the state's Baker Act.

Marie Moore refers to the incident in records she left for police and Shoot Straight, saying she spent a year in and out of a "mental home" but insisted: "I'm not sick." Family members found the audio tapes and three suicide notes late Monday and gave them to police.

"I'm sorry to do this in your place of business, but I had to save my son," one message said. "God made me a queen and I failed. I'm a fallen angel. He turned me into the anti-Christ."

Moore said she could have killed only herself but felt she had to "save" her son and do it in a public way so the world could also be saved. "Hopefully when I die, there will 1,000 years of peace."

Larry Anderson, a manager at Shoot Straight, said it's unclear whether the Moores had been to the range before, but they weren't regular customers. The range requires that customers fill out a form with a series of questions, including whether they have ever been convicted of a felony or been declared mentally unstable. But it has no way to verify the information.

Anderson defended the range's policies, saying: "If someone acts right, we have to assume they are right."

Based on the writings and audio recordings that he's seen in the media, Anderson said, it's clear that Marie Moore was "bent on doing it."

"Sometimes, like what happens Sunday, you have no control," Anderson said. "There's nothing you can do to prevent it."