The man killed himself because he had been marooned on an island and was told he was eating seagull sandwiches, and so when he was rescued he ordered one and when it tasted nothing like what he had been eating, he realized he had been eating something else the entire time, and it was probably his beloved because he had not heard from her on the island, so he killed himself out of remorse.
The man went to a high school whose mascot was the Seagull. His home town treated the Seagull as the entire country treats the Bald Eagle. His whole life he had wondered what was so significant about this creature. He went to college and studied biology, and then went to grad school to get a master's degree in veterinary science. He arrived at this bar on the day he celebrated his completion of his PHD in Seagull studies at Harvard School of Seagulls. The daunting question of his youth still fresh in his mind, he decided there was one final thing for him to do to insure that he had learned all he could about the Seagull. He knew he must eat a seagull to see how it tasted. After tasting this bird he realized why his town and his high school regarded this great bird so highly. He then stormed out and saw somebody eating a seagull sandwich and shot him. For no one shall eat a sea gull sandwich.