A soldier who was shot dead during a live fire exercise was from Dundee, it is understood.
Police are currently trying to establish whether the death was accidental.
The soldier, who has not been named but is understood to be a member of 3 Scots, was fatally injured in an incident involving a firearm at RAF Tain on Tuesday evening.
The base remained on lockdown as detectives from across Scotland converged on Ross-shire to carry out a major investigation, which is likely to last several days.
More than 20 military personnel were taking part in Tuesday’s day-long firing exercise and they will be interviewed as part of the investigation.
Prime Minister Theresa May and First Minister Nicola Sturgeon both paid tribute to the soldier.
Ms Sturgeon said the tragedy is a reminder of the “often difficult and dangerous” work carried out by the armed forces.
The soldier, believed to be male, has not yet been identified but police confirmed they are not local to the area of the incident.
It is thought the soldiers involved in the exercise may have been based with The Black Watch 3 Scots regiment at Fort George.
Chief Inspector Iain Maclelland, area commander for the North Highlands, said the investigation was in its early stages but offered reassurance that there is no wider threat to public safety.
He said: “Police and the Scottish Ambulance Service attended the scene, where one person was found to be fatally injured. There were no other casualties as a result of the incident and next of kin have been informed.
“Both police and the military are providing the family with support at this time and our sympathies are with them at this extremely difficult time.
“Police Scotland is leading the investigation and is working with the Crown Office, procurator fiscal, Health and Safety Executive and armed forces.”
He added that the incident was confined to the firing range.
Ms Sturgeon said: “This is a tragic incident and my deepest condolences go to the family, friends and colleagues of the person who has died.
“It is another important reminder of the often difficult and dangerous job our armed forces do every day.”
Mrs May paid tribute after the tragedy was raised during Prime Minister’s Questions.
Mrs May said: “I, and I’m sure the whole House, would wish to pass on our condolences to the friends and family of the serviceman who has died at the Tain range.”
A number of red flags could be seen flying from poles across the range, serving as a warning that it had been in use.
Two police officers stood guard at the entrance to the site throughout the day.
A grey Volkswagen people carrier containing army personnel was seen exiting the base at about 2pm.
The soldiers inside wore uniforms displaying what appeared to be the 3 Scots badge and The Black Watch red hackles.
About 30 minutes later the same vehicle returned with another two soldiers sitting in the back seats.
Military police were also visible at the entrance to the site yesterday afternoon.
An army spokeswoman said: “We can confirm the death of a soldier at Tain Range Field Firing Area, Scotland.
“It is being investigated by Police Scotland and it is not appropriate for us to comment further.
“Next of kin has been informed and our thoughts are with the soldier’s family at this time.”
