A flower vendor, Subbaiah, 40, was killed and three others sustained severe injuries when a tractor mowed them down at Dumpalagattu of Khajipet mandal in Kadapa district on Monday. The injured, identified as Krishna Reddy, Veeraiah and Subbarayudu, are flower vendors from Dumpalagattu village. They were selling flowers on the roadside when the tractor suddenly swerved off the road and ran over them. They were rushed to the Government hospital at Mydukur, Khajipet police said. A case has been registered.