"It destroyed an entire family," the 19-year-old told CBC News on Monday.
His 49-year-old father, Neil, and 16-year-old sister, Eleesha, were driving home from a Florida vacation at about 2:30 a.m. Sunday when they collided head-on with a suspected drunk driver in a GMC Envoy.
Neil's wife was the third person inside the minivan. She is at Sunnybrook Hospital with serious injuries.
Minutes before the collision, police began receiving calls about a driver going the wrong way down Highway 427.
Wijeratne's family was just 10 minutes away from home, merging onto the 427 from the QEW.
Ontario Provincial Police say charges are pending against the 19-year-old driver, who was arrested at the scene. He had serious but non-life-threatening injuries, police say. Charges are expected to be laid later this week.
The Wijeratne family arrived in Canada from Sri Lanka in 2000. Neil was a maintenance worker at a local hotel. Eleesha was a straight-A high-school student who wanted to study engineering like her older brother.
Wijeratne, who was supported Monday by more than a dozen family and friends who gathered to pray, broke down when he attempted to talk about his father and sister.
"Scared to go see the bodies of my other family members," he said.
But he did want to talk about the 19-year-old alleged drunk driver.
"The only thing I can do is to get the message out about the impacts that you will have if you drink and drive," he said.
OPP numbers show that deaths on Ontario highways are up this year compared to 2011. Since the beginning of this year, 202 people have died on highways, compared to 162 at this point last year.