Calmly, a mother chats to a bystander at a shooting range as her son prepares to fire at a target. Seconds later her son is dead, shot execution-style in the back of the head by his mother, who then turns the gun on herself.

Marie Moore, a woman with a history of mental illness, was able to hire a handgun at a Florida shooting range. Security camera footage of their last moments shows Mitchell Moore, 20, taking aim while his mother stands directly behind him with her gun levelled at his skull before she pulls the trigger.

As he collapsed dead to the floor his mother stepped just out of camera range and shot herself. “I’m so sorry. I had to send my son to Heaven and myself to Hell,” she wrote in a suicide note that was found in her handbag.

Bill McNeil, the deputy police chief, said the case was closed after investigations showed that Mrs Moore had signed a self-certification form at the gun range in Casselberry on Sunday stating that she was not mentally ill — the only requirement for them to rent her a firearm legally. “It’s all done on the customer’s own declaration,” he said, adding: “It’s a political topic that someone will have to take up.”

On Friday Joe Biden, the Vice-President, said that a new approach must be taken to deal with gun violence after a 42-year-old man shot 13 people and himself in upstate New York.

Mrs Moore, 44, had tried to kill herself previously and had spent time in psychiatric hospitals. In a recorded message left behind for her boyfriend she wept and talked about her belief that she was the Antichrist.

Mrs Moore’s ex-husband said she had attempted to commit suicide at the range before and had been barred. A lawyer for the indoor range rejected the claim.

In a second tape marked for police attention Mrs Moore left instructions leading them to a storage facility where she left 63 journals documenting her mental torment.

Police confirmed that Mrs Moore had been committed to protective custody under the Baker Act — the equivalent of being sectioned in Florida — in 2002 over an unspecified incident.

Commercial shooting ranges are not required by law to carry out background checks on customers before renting them weapons.

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