Police in central China's Hunan Province have been investigating three people suspected of breaking management regulations of firearms after a man shot three judges dead and injured three more before committing suicide in a local court office Tuesday.

The incident happened at about 10:05 a.m. Tuesday at Lingling District People's Court in Yongzhou City, said the city's public security department.

The gunman, Zhu Jun, barged into an office on the fourth floor of the court building. He shot the judges in the office before killing himself, police said.

Zhu, 46, was head of the security squad of the China Postal Savings Bank Sub-branch of Lingling District.

Around 7:30 a.m., Zhu took a submachine gun and two pistols from the bank's firearm keeper after saying he would have the guns examined by the higher authorities, police said.

Zhu, who had a son, divorced his wife three years ago. He lived with his parents, an initial police investigation showed.

The investigation showed Zhu committed the attack to take revenge on the court.

Police found that Zhu was angry about the court's ruling on a dispute over the sale of a house in 2006.

This year, Zhu was diagnosed as having terminal cancer. He had been on sick leave at home for two months and only returned to work three days ago, police said.