Who are the people that the Beast Titan turned into titans? In season 3 part 2 episode 13, we see the Beast Titan for the second time in the anime. He suddenly appears with an army of titans who transform with him but who are these people? The citizens of Ragako? The rest of the people that traveled with him to Paradise Island?
The new titans inside wall Rose are the villagers of Ragako. The wiki linked makes this explicit, although the information comes from the Unnamed Final Arc.


   According to Zeke, after having infiltrated Wall Rose, himself, Pieck, and a small group of Marleyan soldiers locate Ragako and choose to target it. The soldiers release a gas diffused with Zeke's spinal fluid and the wind quickly blows it as a fog over the village. Once the subjects of Ymir that inhabit the village inhale this gas, they are paralyzed and etched with a coordinate. Zeke screams, making the paths transform the villagers and allowing him to impose his will on their Pure Titans due to their connection with his Beast Titan.1


In the anime, this is more implied than spelled out. There are a number of pieces of evidence, the most significant of which are; the village is empty, but the horses remain. The village is destroyed, but no blood or bodies are found. And that the trapped Titan looks like Connie's mother.