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While most North Carolinians were remembering the lives lost on September 11, 2001, the Republican leaders in the General Assembly took advantage of a half-empty House and voted to override the governor's budget veto Wednesday morning.
"Republicans called a deceptive surprise override of my budget veto," Mr Cooper said. "Unfortunately, it's the people of North Carolina who lose."
House Minority Leader Darren Jackson, a Democrat, said he told his caucus members that they did not need to be in attendance and that David Lewis, a Republican, chairman of the Rules, Calendar and Operations Committee, gave Mr Jackson his word that there would be no votes, according to the News and Observer.
Republican leaders denied giving any such assurance. The Associated Press reported that the office of Republican Speaker Tim Moore provided audio from Tuesday's floor session of Mr Lewis saying that recorded votes would happen Wednesday.
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Republicans also disputed the claim by the governor and other Democrats that many of them were attending events remembering 9/11 victims and first responders.
Local news reports said only one or two Democrats claimed to have been attending a 9/11 memorial at the time of the vote.
Republicans were unable to override the veto for about two months as long as Democrats were present in the chamber, Mr Cooper said.
The General Assembly needs a three-fifths majority to override a veto, which Republicans lack.
The House is allowed to conduct business as long as at least 61 of 120 members are present. There were 64 members present Wednesday morning.
Jason Saine, a Republican, made the motion to review the budget shortly before 9am and Mr Moore dismissed objections from the Democrats present.
The vote went ahead with the members present. The result was a veto override, 55 to 9.
Democrats in the chamber cried foul, and Jackson later said he wants Mr Lewis to recall the veto before it reaches the Senate.
"This is a tragedy. This is a travesty of the process, and you know it," Deb Butler, a Democrat, yelled before the vote began. "Mr Speaker, how dare you, Mr Speaker!"
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Mary Belk, a Democrat, said at a news conference that Moore "kept talking over us. He turned off our mics," AP reported.
In a tweet shortly after the override, Democratic state Senator Jeff Jackson called Republicans' behaviour "plainly unethical."
As Moore threatened to have Ms Butler removed from the chamber, her Democratic colleagues surrounded her to prevent her arrest, according to video of the confrontation.
Ms Butler told Moore he would have to answer to the people of North Carolina.
"It's a great day for North Carolina," Mr Moore told the local TV outlet CBS 17.
The Washington Post
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