Heat the olive oil and butter in a skillet over medium heat. Stir in the bell pepper and onion; cook and stir until the onion has softened and turned translucent, about 5 minutes. Stir in the garlic, and cook until fragrant, about 1 minute more.
Add the shrimp and cook until opaque, about 2 minutes on each side. Stir in the tomato sauce, parsley, and red pepper flakes, and cook until tomato sauce is warmed through, about 5 minutes. Season with salt and pepper.