I've noticed that there were a noticeable amount of mass shootings or mass murders with a large number of people dead, but the problems is that some cases simply doesn't get a amount of reports on it, resulting in its obscurity, and very vague newspaper articles.
Turkey massacre 1938 - A farmer killed 26 people in Turkey, including 17 women and 4 children. The shooter was killed. Only two newspaper reported about it.
Asureti massacre 1983 - A Ugandan shot dead 21 people at the funeral of a colleague in Asureti, a village near Soroti, Uganda on April 15, before committing suicide.
Taiz massacre 1994 - A Yemeni killed eleven women and seven men, among them his wife and his mother on March 25, before he was arrested by police. When he was led away on March 26 he managed to wrest the gun from a police officer and kill another four people, three of them police officers, before he himself was shot dead.
Nshili massacre 1995 - A Rwandan, a member of the Armée patriotique rwandaise, killed a man after a fight in a bar, and when a group of angered local residents went to view the body of the man at the hospital, were followed by the soldier, who opened fire at the crowd, killing about 14-17 people on November 6.
Zhaodong massacre 1995 - Two Chinese, Feng Wanhai and Jiang Liming killed 32 people and wounding 16 others in Zhaodong on November 18.
The same thing is basically true with machete or knife massacres. There were two massacres with very few reports on it, in the Nainital wedding massacre a drunken soldier killed 22 with a machete. The Siquijor massacre killed 32, but also is one with very limited information, though it is possible that the massacre was just a fabrication by neighbours.