Heat a large heavy Dutch oven over medium heat. Add oil. Cook garlic, onions, celery, and green bell peppers. Cook until softened, about 5 minutes. Stir in cayenne and let caramelize. Add the seafood stock, tomatoes, Worcestershire, hot sauce, and bay leaves. Season with salt and pepper. Simmer for 35 minutes. Add shrimp and cook about 4 more minutes, until they are bright pink and cooked through. Garnish with green onions.