A family returned home from their summer holiday to discover their teenage daughter lying dead inside.
The parents and brother of outgoing Fiona Wilson had to force their way into the house and discovered the 19-year-old's body.
The cause of death of the former head girl at Arbroath Academy, Angus, remains a mystery and has floored her family.
But it has left her mother and father, Ian and Isobel, and her brother, Scott, 15, heartbroken.
Fiona had been working as a swimming instructor and was just days away from beginning a new career as a teaching assistant.
Police say there are no suspicious circumstances surrounding the death on Tuesday.
The family had been on holiday in Fort William and returned on Tuesday.
Her father Ian, 51, said: 'It's totally unexplained. We don't know what happened.
'We were away on holiday with her last week, up in Fort William, and we had a great time.
'She had to go home because she had to work, but she was going to come back up on the Tuesday.
'We tried to phone to get in touch but we couldn't get her. Her gran and granddad came round and couldn't get in, so we rushed back.'
He continued: 'We couldn't get in because the key was in the back of the door, so we had to break in- and that's when we found her.
'She'll be sorely missed. I just can't believe it.
Fiona was described by her family as an active girl who was also a keen dancer.
Mother Isobel, 48, said: 'She was an outgoing, bubbly person. She had taught most of Arbroath how to swim in the last few years.
'A lot of kids would know her from teaching them to swim, and she did the Angus Musical Youth Theatre as well. She was very active.
'She had just finished a year at college training as a teaching assistant, which she passed.
'She loved working with kids and she wanted to be a primary school teacher.
'She was offered a job as a classroom assistant with Dundee council which she was due to start next week, which she was looking forward to and was excited about.
'We just need to know why this happened.'
A spokeswoman for Tayside Police said: 'I can confirm officers attended the sudden death of a 19-year-old woman at 11.30am on Tuesday.
'There were no apparent suspicious circumstances but, as with all sudden deaths, a report will be submitted to the procurator fiscal.'
A Spokesman for Dundee College said: 'We are shocked at this sad news.
'It is truly tragic when someone so young, with so much potential, dies.
'Our thoughts are with Fiona's family.'