How did slaves in Texas gain their freedom? Why were some former slaves fearful after learning of their freedom?

The history of slavery in Texas, as a colonial territory, then part of Mexico, later Republic in 1836, and U.S. state in 1845, began slowly. The use of slavery expanded in the mid-nineteenth century as White American settlers, primarily from the Southeastern United States, crossed the Sabine River and brought slaves with them. Slavery was present in Spanish America and Mexico prior to the arrival of American settlers, but it was not highly developed, and the Spanish did not rely on it for labor during their years in Spanish Texas.