WFAA-TV, Dallas

DUNCANVILLE, Texas — Duncanville teacher Vinita Hegwood, who resigned less than a week after her controversial tweet about Ferguson prompted a social media firestorm, has been fired by the school board.

The Duncanville Independent School District Board of Trustees voted unanimously Friday to immediately terminate Hegwood's contract.

"Our focus at Duncanville ISD is educating our more than 13,000 students. Our 794 teachers have been and will continue to engage in the business of educating our students." the trustees said in a statement.

The tweet, sent Nov. 7 from Hegwood's personal Twitter account, referred to Ferguson, Mo., where rioting occurred after the fatal shooting of unarmed black teen Michael Brown in August. The town is awaiting a decision by the grand jury into Darren Wilson, the white police officer who killed Brown.

"Who the (expletive) made you dumb duck (expletive) crackers think I give a squat (expletive) about your opinions about my opinions RE: Ferguson? Kill yourselves," the tweet read.

The tweet went viral and prompted accusations of racism and demands for action against Hegwood. It isn't clear whether there was a tweet aimed directly at her that prompted the outburst.

On Monday, the school board placed Hegwood on administrative leave without pay. Hegwood, who is African American, taught English, according to the Duncanville High School website.

Thursday, Hegwood announced her resignation in a statement released by the Texas American Federation of Teachers.

In the statement, Hegwood said her tweet was a reaction to "a series of threatening and racist attacks" made toward her on Twitter during a debate over the Ferguson incident.

"My reaction in no way reflects the standards to which I have held myself and my students for the last 20 years of teaching," she wrote. "I accept full responsibility for my actions, and I regret the embarrassment that it has caused the school district."