ST. PAUL, Alta. -- Richard Benson wasn't supposed to be driving. But court records show he had been behind the wheel for about a decade.

The Alberta man had been told by doctors that he needed medication to prevent his recurring seizures. But he rarely filled his prescriptions or swallowed the pills.

A newly released court document confirms what Benson's family had earlier suspected -- he was having a seizure when he lost control of his minivan and crashed at high speed through the wall of a rural Alberta school one year ago.

The vehicle landed in a lower-level Grade 6 classroom at Racette Junior High in St. Paul, pinning three girls underneath.

One of the girls, 11-year-old Megan Wolitski, died in hospital the next day. The court document -- an agreed statement of facts filed with the court and obtained by The Canadian Press -- reveals two others have suffered long-term effects -- one is unlikely ever to get better.

"Maddie Guitard sustained lifelong debilitating injuries," says the document. "She remains in a vegetative state" and the document says she is not expected to recover "and have a regular life."

Angelina Luce suffered a traumatic brain injury and has speech and eye problems, the document says. She continues to get therapy for emotional issues.

Benson, 47, pleaded guilty in court earlier this month to one count of criminal negligence causing death and two counts of criminal negligence causing bodily harm. He remains in custody and is to appear in court for a sentencing hearing in November.

Defence lawyer Jason Conlin says his client wanted to spare the families of the girls and the community the ordeal of a trial.

"He's always expressed remorse and simply did not ever intend that day to go as badly as it did."

Relatives earlier said the single father of nine children had been severely beaten in 2002. The attack put him in a coma and left him with a metal plate in his head.

The court document says the assault left him permanently vulnerable to seizures and he was prescribed anti-seizure medication.

The following year, Benson applied for a driver's licence, but did not declare that he had physical or health problems that might affect his ability to drive. The province requires people to disclose such information and their applications are often denied.

While filling out a form in 2006 to receive government assistance for the severely disabled, Benson admitted he was prone to seizures and claimed he was taking drugs to control them.

"I need to take Dilantin on a regular basis or I will have seizures, fainting, blackout(s)."

When he applied for another driver's licence and auto insurance in 2011, he again failed to mention his health. In the spot where he was supposed to acknowledge any physical or medical conditions, he wrote "none."

The court document details several of his seizures, hospital stays and prescriptions from doctors. It says the seizures had been increasing in frequency over the years.

Benson "continued to drive while being aware of the danger or risk he posed to the lives or safety of others while operating a motor vehicle."

On Oct. 21, 2012, he had a seizure at home, but didn't go to a doctor. His worried family told him he shouldn't be driving. Four days later, he drove his van into the school.

He had just dropped his two youngest children off at their different schools in St. Paul, then stopped at the local post office. He was driving away, down a back alley, when he had another seizure, says the court document.

The van bolted at about 80 km/h down several more back lanes, crossed five streets and nearly caused two accidents before it headed straight into the school.

Benson was arrested at the scene. Witnesses initially believed he was drunk.

The court document says tests showed he had no alcohol in his system. But they did reveal his body contained little of the medication he was supposed to be taking. The amount was equivalent to a single recent dose rather than an ongoing regime of the drug.

Conlin says he's at a loss to explain why his client lied on his driver's licence applications and didn't take his medication.

"He doesn't have a very good recollection of a lot of events. He's got a very short term memory, to the point where I could have a conversation with him one day and have the same conversation with him the next."

Glenn Andersen, the mayor of St. Paul, knows the families of all three girls. Everyone in the small town of 6,000 knows them or the other 10 children who had been in the classroom that day.

"It's very difficult for the entire community," said Andersen. "Nothing but time can make this go away."

-- By Chris Purdy in Edmonton