RAF policeman Cpl Brent McCarthy, from Telford, and Welsh Guard Lance Corporal Davies were just "in the wrong place at the wrong time".
Speaking at the inquest into their deaths at Oxford Coroner's Court, Lieutenant Benjamin Bardsley said he believed their shooting was an "opportunist event" as no one had been told in advance they were going to be in the area.
They died in what is known as a green- on-blue attack - killed by the Afghan personnel they were mentoring. It is also known as an insider threat.
The insider threat at this time was very, very low.
The risk was deemed as low because it had not happened for a long period of time.
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Salih Khater has been charged with the attempted murder of members of the public and the attempted murder of police officers.