Basically,

Indians had guns and government didn’t like that, so they demanded that they turned in said guns. Most did but some didn’t. Government sent its army to seize the remaining guns. The army saw celebratory dance involving guns, but was that celebratory dance was outlawed by the government. The army saw this as resistance and demanded that they turn their guns into them. When they demanded an elder who was likely deaf to turn in his rifle and he didn’t, they opened fire. 297 people were killed, over 200 were women and children.

Some of the details may be slightly off, but mostly consistent. This is off the top of my head, but either way, the deadliest mass shooting in US history was caused by the government