Mr Slinn had been travelling home from Dorset with his family at the time
A head teacher was unlawfully killed when his car was hit by a speeding van overloaded with beer barrels on a motorway, a coroner has ruled.
Daniel Slinn, 44, who worked at Calshot Primary School, in Birmingham, died in the six-car pile-up on the M5 near Tewkesbury, Gloucestershire, in May.
The van driver Harbinder Singh Dosanjh, 36, and his wife Manjit Kaur Dosanjh, 35, from Coventry, also died.
The inquest in Gloucester also ruled Mrs Dosanjh was killed unlawfully.
Gloucestershire coroner Alan Crickmore recorded a verdict of accidental death for Mr Dosanjh, who had been travelling at between 85mph to 90mph before the crash on 30 May.
The hearing was told one of the tyres blew on the white van, causing it to flip over the central reservation of the motorway.
It then hit Mr Slinn's Mitsubishi Colt, which had been travelling in the opposite direction.
The van's load of beer barrels was 218 stone (1,285kg) overweight.
The van then shed its load causing kegs to litter the carriageway, witnesses told the inquest.
Mr Slinn's wife Lisa, 42, and 11-year-old daughter Carrie were also injured in the crash which happened when the family, from Edgbaston, had been travelling home after spending the half-term school holiday in Dorset.
A total of 15 people suffered minor injuries in the pile-up.
Mr Slinn had been writing a children's book that his family said "could be the next Harry Potter".
His wife and children have now vowed to finish it for him.
After the inquest Mrs Slinn said: "Daniel was a wonderful husband, father and head teacher who was killed due to the careless driving of another individual.
"Whilst we are sorry for the loss suffered by his family, it is clear that Dan would still be alive today if that driver had acted more responsibly."
Mr Dosanjh's brother-in-law Jaskaran Singh Rama said: "We regret what has occurred and would like to express our condolences to the family of Mr Slinn."