New Zealand’s intelligence agency has confirmed for the first time that a teenager tried to assassinate Queen Elizabeth II during a visit to the southern city of Dunedin in 1981, sparking a police inquiry into how the incident was handled.

Documents released by the New Zealand Security Intelligence Service (SIS) show the then 17-year-old Christopher Lewis shot at the Queen as she got out of her vehicle on the way to a science fair on 14 October during her eight-day tour of the Commonwealth nation.

“Lewis did indeed originally intend to assassinate the Queen, however did not have a suitable vantage point from which to fire, nor a sufficiently high-powered rifle for the range from the target,” said a 1997 SIS memo, that was declassified in February and sent to Reuters on Thursday.

The documents were declassified in response to a request by Fairfax Media.

Lewis, who intelligence documents described as a “severely disturbed” youth, was not charged with attempted murder or treason, adding to claims the incident was downplayed to prevent embarrassment to a country hosting a royal visit.

He was instead charged with unlawful possession and discharge of a firearm.

Members of the crowd in Dunedin and reporters heard the shot, but were initially told by police that the noise was from a falling sign or a car backfiring.

“Current police investigations into the shots have been conducted discreetly and most media representatives probably have the impression that the noise was caused by a firework of some description,” said a November 1981 memo from SIS, also released on Thursday.

According to intelligence documents, police kept a close eye on Lewis during a 1986 visit by the Queen to New Zealand, fearing that he was still a risk.

The intelligence agency revelations have prompted a police inquiry into the matter, authorities said on Thursday.

A New Zealand police spokeswoman said in a statement to Reuters that the police commissioner had ordered the case file be examined.

More than a decade after the incident, Lewis was charged with the brutal murder of an Auckland mother and the abduction of her baby daughter, who was later dropped at a nearby church.

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According to multiple news reports at the time, Lewis electrocuted himself while in prison in 1997 awaiting the murder trial. He denied the murder charge in a suicide note.

New Zealand has been independent of British rule since 1947, but retains the Queen as its constitutional monarch and head of state. She has visited the country as monarch 10 times, most recently in 2002.