Four persons, including two schoolchildren, were killed and six others injured in three lighting strikes in West Bengal's South 24 Parganas district on Sunday, police said.Two schoolkids and a fisherman died when lightning struck them while playing football in Mahishmari area of Sagar island. Five others were battling for their lives in serious condition in a rural hospital.One fisherman was killed in the Patharpratima community development block.Another person sustained serious injury in Raidighi community development block when he was struck by lightning.