"Last night, despicable crimes were committed against Dallas police officers, and when the dust settled, five of them were dead as a result of an organized execution by criminals who possessed guns and used them to the extreme," Butterfield stated.
Five Dallas police officers were shot and killed on Thursday night following a peaceful demonstration by the Black Lives Matter civil rights movement. Two civilians and seven additional police officers were also shot but are expected to survive.
The protest was one of dozens held in the United States after two African-American men were shot and killed in two days by US police.
Butterfield explained that 491 people, mostly African-American, have been fatally shot by US police officers as of June 30, compared to 465 during the same time last year.
Earlier on Friday, US President Barack Obama said the deadly attack had been calculated and pledged that anyone involved in the shooting would be held accountable.