The lieutenant noted that the Kurdish militias fought their own civil war from 1993 to 1998, a conflict that left thousands dead.
"You will be killed," it read, for collaborating with the Kurdish militias.
One Arab woman, a teacher, said Kurdish militias were coming into neighborhoods at night and firing guns to scare people away.
There were Kurdish militia in the region.
The Kurdish militia, the peshmerga, is estimated to number upwards of 50,000.
It is thought that Kurdish militias now control at least four main towns and cities in northern Syria.
Iraqi Kurdish militias had little choice but to cooperate with Turkish operations in northern Iraq.
The bomb also injured six Americans and two members of the Kurdish militia who were guarding the American facility, he said.
He said the Kurdish militias were a "separate" question, but did not elaborate.
Coalition forces also supported Iraqi Kurdish militia, estimated to number upwards of 50,000.