Leone and his wife Amber celebrated the birth of their first child, Tal Gunner, this spring. Schexnaider said that Leone left to rejoin his wife, who never made the permanent move to Louisiana.
Leone doesn't have a job lined up yet, Schexnaider said.
"It was a tough decision for him," ULM coach Jeff Schexnaider said. "Even though it's a no-brainer decision, he enjoyed his three years here."
Leone, who played at the University of Texas as a collegian, was in charge of ULM recruiting.
"He was real crucial in recruiting and handling our pitching," Schexnaider said. "He was part of the reason for our success as we made the transition to the Sun Belt Conference. We hate to see him go."
The search to replace Leone is underway. Schexnaider interviewed a candidate from a Southeastern Conference program in his office on Wednesday.
"It's huge," Schexnaider said of making a good hire. "This year coming up, we've got 14 seniors. The next recruiting class is going to be really crucial to replace six position starters probably and five or six pitchers.
"That's one of the things we're looking at. We want someone who can fit in with the staff and make us better. And it doesn't necessarily have to be a pitching coach."
Schexnaider said ULM's staff is equipped to handle pitching if that isn't the next assistant's area of expertise.
Leone came to ULM following a lone season at Seminole State College. Before that, he spent one year as an assistant coach at St. Gregory's University before moving on to Seminole State.
His coaching career began at East Central University (Okla.), his alma mater. The Shawnee, Okla., native earned a bachelor's degree from East Central in 2001 and a master's degree from ECU in 2004.