A family of six drowned in a van on Sunday while trying to escape flooding from Hurricane Harvey, three of their relatives told Houston's KHOU 11. The family included four children ages 16, 14, 8, and 6, as well as their great-grandparents, ages 81 and 84. Witnesses told the station that the van was swept into high waters. The children's great-uncle, who was driving the van, survived by grabbing a tree limb and escaping the van. But the children and their great-grandparents were unable to exit through the van's rear door as the vehicle sank. Authorities have yet to confirm the deaths, which would be the single deadliest known incident of the hurricane so far.