An investigation into how a trainee police call centre operator was shot in the chest at a firearms awareness course may last up to three months.

Keith Tilbury, 50, was accidentally shot with a .44 Magnum at the course held at Thames Valley Police headquarters, in Kidlington, on Wednesday.

Other call centre operators on the course rushed to give him first aid before he was taken to hospital.

According to a national newspaper, a firearms instructor, Pc David Micklethwaite, has been temporarily redeployed to non-firearms duty. The Independent Police Complaints Commission (IPCC) has launched an investigation and seized the revolver for tests.

A IPCC spokesman said they could not comment on the content of the investigation.

The spokesman added: "We will not get into details at this stage of the investigation.

"The length it takes particularly depends on whether it goes to the Crown Prosecution Service (CPS).

"We could be talking anything up to three months."

The results of the investigation will be passed to IPCC commissioner Deborah Glass who will decide whether there were any criminal or disciplinary breaches and if the CPS will be called in.

Maurice Collins, of the Police Federation's Thames Valley Branch, which is a representative body for all officers below the rank of superintendent, said the federation could not comment while an investigation was under way.