Speaking at FMQs, Ms Sturgeon said the case, which has been referred to the Procurator Fiscal, needed to be fully investigated but added: "What is reported is unacceptable and I am in no doubt about that.

"Our ambulance service is working under acute pressure right now largely due to Covid."

Ms Sturgeon said paramedics and ambulance staff are working "heroically", but confirmed that the Scottish Government is now looking to bring in military assistance to ease pressure on waiting times.

She said: "I recognise that some people are not getting the standard of service that they should be getting or the standard of service that the ambulance service want to deliver.

"That is not acceptable and I apologise unreservedly to anyone who has suffered or who is suffering unacceptably long waits.

"A range of actions have already been taken to address these challenges - for example additional funding to support new recruitment.

"A number of other actions are also under active consideration...and I can confirm now that this includes consideration of seeking targeted military assistance to help deal with short-term pressure points.

"Such military assistance is already being provided to ambulance services in England and of course we have had military assistance for other aspects of the pandemic over the past 18 months."

Ms Sturgeon said she would personally be meeting with ambulance service and that Health Secretary Humza Yousaf will make update to parliament next week on the ambulance service.

It is understood the support could include use of military ambulances and vehicles and will be made as a Military Aid to Civilian Authority (MACA) request - as the vaccine delivery was - with a potential to extend into winter. 

A spokesman for the First Minister told media the arrangement would go on "as long as it's necessary and appropriate for clinical care".

READ MORE: Anger as Glasgow father-of-three dies after 40-hour wait for ambulance

Scottish Conservative leader Douglas Ross pressed the First Minister to admit that the ambulance service "is in crisis" as he said over the past week "every day we have heard of tragic, life-threatening waits for ambulances". 

In addition to Mr Brown's case, he cited the case of 86-year-old Lilian Briggs who lay on her kitchen floor with a broken hip for eight hours waiting for an ambulance and a BBC Scotland phone-in caller whose husband had waited 23 hours with heart attack symptoms. 

Ms Sturgeon said extra funding was being used to recruit an additional 300 paramedics and technicians, and that a "range of additional actions" were also being considered including more support for rural ambulance stations, alternative transport arrangements for lower risk patients, and temporary admission wards to "ease the bottleneck" at A&E which has been leading to ambulances queueing up outside emergency departments while they wait to transfer patients. 

This has been blamed for knock-on delays for patients waiting for ambulances, while a surge in calls to 999 - around 10,000 a month up on last summer - is putting pressure on call handlers trying to triage cases according to priority. 

Ms Sturgeon said: "The fact that anyone in our country waits an unacceptable period of time for an ambulance when they need urgent care is not acceptable and that is why we will closely and intensively with the ambulance service to support it to meet those challenges, which I would expect to continue for a period as the Covid pressure continues and of course as we go into the winter." 

The First Minister also defended Health Secretary Humza Yousaf, after he was criticised for saying people should "think twice" about calling 999 unless it was "absolutely critical". 

READ MORE: How have you experienced ambulance and A&E waiting times? Let us know

She said: "Where people require interventions from the health service which would better come from a part of the service other than the ambulance service then we should encourage them to do that.

"Where people consider that they need an ambulance they should never hesitate in calling an ambulance if that is the intervention they think is required. 

"As First Minister let me be very clear: the ambulance service is there to provide emergency assistance to those who need it. It is facing the the most intense challenges and some people are not getting the service that they should be. 

"But the answer to that is for Government and the service to work to make sure that they are meeting that so that anybody who does need an ambulance doesn't feel that they should hesitate to phone and ambulance and just as importantly, they get the ambulance timeously as they have a right to expect."

However, Scottish Labour leader Anas Sarwar accused the First Minister of trying to "hide behind the pandemic", citing pre-Covid statistics of 1000 cases where ambulances had waited over two hours outside hospitals to transfer patients and 15,000 times where an ambulance took over two hours to arrive, along with a pre-pandemic staff survey which found that 63% felt the ambulance service was already short-staffed.

"Please do not use the pandemic as a cover for your Government's failings," said Mr Sarwar.

"The truth is this is an avoidable human tragedy on a heartbreaking scale."