VISAKHAPATNAM: A father and his son travelling on a two-wheeler were killed when a speeding lorry knocked them down from behind at Duvvada Junction near Gajuwaka on Tuesday. E Sanjeeva Rao (40), a Steel Plant employee, and his seven-year-old son Srinivas died on the spot. Tension prevailed at the accident spot as the employees of steel plant conducted a rasta roko in protest against the mishap.