A learner driver has been charged with killing a pedestrian after a car ploughed into a group outside a popular Melbourne comic convention. A 20-year-old man died and another man the same age was seriously injured when a Toyota sedan mounted the kerb outside Melbourne Showgrounds in Ascot Vale just before 5pm on Saturday. An off-duty officer and bystander intervened and arrested the driver after the car struck the duo and continued along the footpath, police said.