Chop the peeled and deveined raw medium shrimp into 1/2-inch pieces.
In a large glass or non-reactive bowl, combine the chopped raw medium shrimp, fresh lime juice, and fresh lemon juice. Ensure the shrimp is fully submerged in the citrus juices.
Cover the bowl and refrigerate for 30 minutes, or until the shrimp turns opaque and pink, indicating it is cooked by the citrus acid.
Remove the bowl from the refrigerator. Gently stir in the diced Roma tomatoes, finely chopped red onion, jalapeño, chopped fresh cilantro, kosher salt, and black pepper.
Cover and refrigerate the mixture for an additional 15 minutes to allow the flavors to meld.
Just before serving, gently fold in the diced avocado to maintain its shape and vibrant color.
Serve immediately chilled with tortilla chips.