Watch: Dallas Cowboys' Marshawn Kneeland Dead at 24, Days After Scoring First TouchdownMarshawn Kneeland's teammates are mourning a tremendous loss. After the Dallas Cowboys defensive end's unexpected death at age 24, quarterback Dak Prescott expressed his grief in an emotional reflection. "It's been a very tough day," the NFL player-who joined the Texas-based team in 2016-told CBS Sports Texas Nov. 6. "Tragic loss, I hurt-heavy heavy heart today. I hurt for Marshawn, I hurt for his family. I hurt for his girlfriend. I hurt for every single one of my teammates.