There were two seperate attacks on that day.
First one was an attack on railroad workers that were participating in the CDM movement. The following video was taken from one of the apartments. These were hired thugs by the military, armed with metal rods, slingshots and knifes. Some of the photos show proof of one of those thugs getting out of the cop car.
The second attack took place later during the day. The military paid people to come and join their rally. The videos below contain an interview with a 18 year old kid. He confirmed that he does not even know what was happening. They just paid him money to join along. The police originally blocked the main road to prevent pro-democracy protestors from marching, yet when the pro-military crowd arrived, they not only removed the blockades but also stood with their shields to "protect them from pro-democracy supporters".
Eventually, several armed thugs came running out and started stabbing and beating innocent bystanders. The same cops that were blocking the road just stood and watch.
The photos of books are proof that these people are hired and paid for by the military. These books were taken from some of the thugs who were captured by the people. They contain payment information.