A 53-year-old man shot dead by police in an isolated Cornish village was carrying a Samurai sword.
IPCC investigators are at the scene
The Independent Police Complaints Commission (IPPC), which was called into investigate the shooting said it may be "crucial" evidence.
Philip Prout was shot early on Tuesday by armed police called to a house in Lewannick, near Launceston.
Mr Prout was shot after a four-hour siege which began when officers were called to a domestic incident.
An eight-strong team from the IPCC is already in the village carrying out inquiries aided by officers from an outside force.
IPCC Commissioner Ian Bynoe, responsible for Devon and Cornwall, said: "The emerging picture is that Mr Prout was in possession of a number of bladed weapons, a long Samurai sword, and two smaller weapons including a martial arts dagger.
"It is a crucial piece of evidence if that is the case.
"It may affect the justification for actions in the way the incident was commanded and the way tactics were used by officers."
An inquest will be opened on Friday in which the IPCC may be giving evidence.
The statement follows calls for more information on the killing by local MP Paul Tyler, a former member of the Devon and Cornwall Police Authority.
Dozens of police were called to the village at 2100 BST on Monday to deal with what was said to be a domestic incident with reported threats of violence.
Devon and Cornwall police negotiators were at the scene when Mr Prout was shot at 0125 BST on Tuesday.
"Emergency treatment was administered at the scene, but the man later died in Derriford Hospital, Plymouth," said a police spokesman.
The Devon and Cornwall force referred the matter to the IPCC and on said on Wednesday that it supported the Commission's investigation.
Deputy Chief Constable Nigel Arnold: "We are following the press and public interest in this story, and we have asked the IPCC to release as much information, at the earliest opportunity, to the family and community, as possible, without compromising their investigation."
Mr Prout is believed to have recently moved to the area from Crawley, West Sussex.
It is not yet known whether there was anybody else in the house at the time of the shooting, or how many shots were fired.