The two worked together on the highly acclaimed drama Apollo 13 in 1995. Below is Howard's emotional letter in its entirety:
Unlike the Twisters he famously chased in the movies, Bill Paxton was the kind of force of nature you ran toward and never away from. He energized every situation with his humor, his intelligence and his appreciation of the moment he was inhabiting and the people he was inhabiting it with.
He had charm and an admirable Joie de vivre — Texas-style. He was both down-home and a serious fine-art enthusiast and collector. Bill was playful-yet-dutiful in his work as an actor, and likewise capable of being a strong and serious leader when directing a challenging scene on a movie set.
He loved adventure, and no one was happier than Bill when we were filming our zero-G scenes for Apollo 13 out over the Gulf of Mexico in NASA's KC-135, nicknamed The Vomit Comet. For the record, Bill never lost his lunch through all those weightless scenes. But when a floating camera operator shooting a close up of Bill got sick and projectiled, Bill floated over to me at my director's monitor wearing an unimaginably huge grin and said, "You gotta see this, Ron. I got puke in my hair, man! Cool!"
He knew production time on the plane was precious so within seconds he had toweled off his head and was 100 percent focused on the next take and his job playing an astronaut who was giving his all to help his compatriots survive and get home.
Bill will be agonizingly missed by friends and fans alike.
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For more on how Paxton's friends and co-stars are coping with the news of his death, watch the video below.