All that changed during his teenage years. Mitchell began using drugs, his school marks deteriorated, he stole money from home and he broke into cars.
His father took him to several counsellors, but he dropped in and out of various schools and treatment programs in British Columbia and Alberta and his erratic behaviour escalated. Mitchell landed in jail, estranged from his family.
The troubled young man's downward spiral ended in tragedy in May 2012. After Mitchell killed two people at a Burnaby restaurant and wounded a third, he was shot dead by police in Maple Ridge, east of Vancouver. He was 26.
"If things could have happened differently, we would have gotten to a different conclusion ... and this would have been prevented," Mitchell's father David told a coroner's inquest Thursday. "Or, if we could have forced Angus, as a family, to a thorough 30-day psychiatric assessment, it could have been prevented."
As David Mitchell recalled his son's troubled past, photos displayed on a projector screen showed a smiling boy with blond hair. In one, he grinned as his held a dog in his arms.
David Mitchell, a financial manager and former lawyer, said when his son's alarming behaviour started getting worse, he should have realized it was more than just somebody being unco-operative during his hormonal teenage years.
As Angus Mitchell got older, the drug use intensified and he landed in jail in Alberta for threatening a man with a knife, stealing alcohol and breaking a car's rear-view mirrors. David Mitchell, not wanting his son's life to be tainted by a criminal record, managed to get the charges stayed.
In 2010, when Angus Mitchell started sending his father and sister angry emails that included death threats, David Mitchell said he knew he had to show them to the RCMP.
"They were delusional, abusive emails and they went to mental health issues from my perspective," he told the inquest.
The RCMP filed the emails under "unsubstantiated trespass," he said.
David Mitchell said he appealed to friends and police for advice on how to get the psychiatric help he thought his son needed, but what he heard only added to his sense of helplessness.
"Everybody said we need a triggering event. We need some precipitating event which would allow the court to order him to have this assessment," he said. "I wondered what that triggering event would be. I thought it would be a common assault situation, and of course, the horror ... look what's happened."
Mitchell was surrounded by police in Maple Ridge after they warned the public that he was suspected of a double murder and an attempted murder. A paramedic team was stationed at the scene. Matthew Singleton, a paramedic with basic training in life support, was at Mitchell's side moments after he was shot at least 10 times in the chest, back and pelvic area.
Singleton told the inquest that Mitchell appeared conscious at first, but suffered a heart attack and his breathing and pulse stopped. An advanced life support paramedic arrived minutes later. John Chambers said he saw that Mitchell had severe damage to one side of his lungs and there was no blood flow to his heart. Even as he administered CPR and injected fluid to make up for the blood loss, Chambers said he knew Mitchell would not make it.
"Quite honestly, I thought there was no chance he would survive."
Mitchell was flown to a trauma hospital in New Westminster, about 30 kilometres away. A trauma doctor and his team in the emergency room worked on Mitchell for about 10 minutes, but it was no use.
"He was not moving, his eyes were closed, he was not breathing on his own, he had no pulse, and when I placed an ultrasound machine on his bedside to examine his heart ... his heart had stopped," said Dr. Neil Barclay. "In a situation like this, we know that the chances of surviving is zero, there is no chance of survival. So at that point, we decided to terminate care."
After Mitchell's death, RCMP revealed that not only had he killed 36-year-old Huong (Andy) Tran and 34-year-old Chinh (Vivian) Diem Huyhn and wounded his former landlord, he was also planning to target six businesses and six people across Metro Vancouver.
The police officers involved in the shooting have been cleared of any wrongdoing.
Earlier in the inquest, jury members heard that Mitchell had a history of mental health issues and substance abuse, and that the agency responsible for firearms licences approved his gun application without delving into his medical history.
Months before he was killed, Mitchell was arrested after walking into a Saanich doctor's office with a rifle. The rifle, eventually used to kill his victims, was returned to Mitchell after a Victoria hospital psychiatrist discharged him.
Jury deliberations are to begin Friday.
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