Bow echoes are where part of a squall line starts pushing out ahead of the rest of the line.
A simple explanation is because of wind flow into and out of those particular cells, and what this causes is those cells pushing out ahead very rapidly. Bow echoes, besides causing very heavy downbursts and wind gusts, tend to be self-sustaining. The storm that hit Starkville had its beginnings in northern Louisiana. As the squall line pushed east, it caused sporadic damage, except for a tornado near Durant, MS which caused one fatality. As the squall line approached the Starkville area, the northern section started taking on bow echo characteristics, and began rapidly moving east, causing very heavy winds and some significant areas of damage, mostly to Starkville and western Lowndes County.