WELLINGTON, New Zealand -- A troubled teenager who wanted to assassinate Queen Elizabeth II during her 1981 visit to New Zealand fired a shot near her motorcade, newly released documents show.

New Zealand's internal spy agency the Security Intelligence Service released the previously classified documents to the news website Stuff, shedding new light on the historic incident.

The documents say 17-year-old Christopher John Lewis wanted to kill the queen but didn't have a good vantage point or a sufficiently high-powered rifle. He fired a single wayward shot which likely passed above the crowd.

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At the time police told journalists who heard the noise that it was a sign falling over, and later said it might have been firecrackers. Police appeared to downplay the seriousness of the incident, and only charged Lewis with possessing and firing a weapon in public.

Colin Peacock of Radio New Zealand told CBS News partner network BBC that the seeming efforts to keep the incident quite fit a pattern of the time.

"Since these articles came out in January other media organizations and journalists have come forward and said that they do recall the police visiting them and telling them in no uncertain terms they were not to report anything about any shot or any sharp sound that was fired. So they do believe this came from the very very top and shut down the story," Peacock told the BBC. "Unfortunately at that time in New Zealand history, there are some cases of police investigations where they were not forthcoming at all about the truth and things were covered up so there could be a pattern there and that's probably why the police service today is taking this seriously and now reopening the investigation."

Lewis would later kill himself at age 33 while in prison awaiting trial on murder charges in an unrelated case.

When questioned by police at the time, Lewis claimed to be part of a group called the National Imperial Guerrilla Army that was carrying out terror operations. He said there were two other members called the Snowman and the Polar Bear, but later admitted he'd made them up.

The documents say police found a .22-caliber rifle with a discharged cartridge on the fifth floor of a building after Lewis told them it was there.

"Lewis did indeed originally intend to assassinate the queen," the documents say, "however did not have a suitable vantage point from which to fire, nor a sufficiently high-powered rifle for the range from the target."

The documents say the angle of fire and range would have made it difficult for Lewis to shoot the queen, and that buildings would have screened her for all but a few seconds.

During a later visit by the queen, according to Stuff, police were so worried that Lewis might make another assassination attempt they paid him to go on a 10-day vacation to a remote island. They gave Lewis free accommodation, daily spending money and the use of an SUV.

The news website said people close to the case thought Lewis got off lightly due to political interference and worries that New Zealand would lose future royal tours due to the security lapse.

Police said they would re-examine the case file in light of the interest in the case.