Grilled Lobster and Avocado Cocktail

2 tablespoons prepared horseradish, drained

1 tablespoon Worcestershire sauce

1 teaspoon hot sauce

1 tablespoon finely chopped fresh tarragon leaves

Salt and freshly ground black pepper

1 ripe Hass avocado, peeled, pitted and finely diced

1/2 small red onion, thinly sliced

1/4 cup chopped fresh cilantro leaves

2 (8-ounce) lobster tails, parboiled and flesh coarsely chopped