It was Razzle & Dazzle. Dazzle has a dark stain on his left cheek, possibly ichor. Dazzle also says "(Help pls...)" Proving that he saw Razzle kill Astro. Razzle says "Astro? I wonder who killed him... " and he doesn't hide his expression. RnD was the only one who also questions who did it; unlike Dandy and Toodles. Razzle also has something seemingly black in his hand, maybe ichor? Or maybe he's hiding a knife in his hand and we only see the tip covered in ichor, and a knife was one of the weapons, and Astro's body has text carvings cut into him.

Dandy