Christopher Thompson, 35, was shot to death last January inside his barbershop at Malvern Town Centre.
Kevin Perez entered the guilty plea, admitting he pulled the trigger on the shotgun and killed Thompson after the barber pulled out of a $300 deal.
"He didn't do nothing to that guy," said Michael Thompson. "My brother got killed for what? For what?"
In court Perez said it all started with a dispute over stolen computers.
Thompson had planned to buy some from Perez for $300. But one of the laptops was broken and Thompson backed out of the deal.
Perez showed up with a shotgun, planning to intimidate Thompson. He ended up shooting him, firing over and over as Thompson tried to get away.
Both Perez and his brother Chris were charged with first-degree murder but on Friday the charge against Chris was withdrawn.
Police say the man going to prison is the only one responsible for the slaying.
"We know we have the right person who committed this crime against Chris Thompson," said Toronto police Det. Leslie Dunkley.
Perez will go to jail for life with no chance of parole for 20 years.