He was the guy next to Oswald when he got shot.
https://www.nbcnews.com/news/us-news/jim-leavelle-lawman-lee-harvey-oswald-s-side-dies-99-n1048251
https://www.nbcnews.com/news/us-news/jim-leavelle-lawman-lee-harvey-oswald-s-side-dies-99-n1048251