Prior to his death, Jonsson was a rapidly improving sprinter who competed over 100, 200 and 400 metres. He broke the Swedish national record six times over 200 metres, his strongest event. He became European Champion over that distance at the 1962 European Championships in Belgrade, setting a new championship record in the final with a time of 20.7 seconds. Less than two weeks after winning in Belgrade, Jonsson died in a car accident on the road between his hometown, Växjö and Alvesta. A street near the athletics track in Växjö is named after him. Aside from athletics, Jonsson also played ice hockey and bandy for Nässjö IF.