It was only when the first book hit the bottom of a cardboard box that he realized — “this is it.”

June 30 will mark the end of Dean James Keith Motley’s 30-year term at Northeastern University as a former undergraduate student and administrator. Motley is moving on to become the Vice Chancellor for Student Affairs at the University of Massachusetts, Boston. The position is very similar to that of the Vice President of Student Affairs at Northeastern, which will be left vacant once Karen Rigg, the current VP, retires in the fall. A replacement has not been named yet.

“This is a tremendous opportunity for him, one that he certainly earned and deserved,” said Dean of Student Life Ron Martel. “I think he leaves behind a legacy that I doubt will ever be replicated.”

Dean Motley will begin the next chapter of his professional career on August 4. Motley said that if he did not make the transition quickly, it may have never happened.

“Northeastern has always been a center for me,” he said, commenting on his five years as an undergraduate and his 25 years as an administrator and part-time basketball coach for the university. “I have a lot of pride of what I have accomplished here as a student and as a professional. I never thought I would be here all these years.”

UMass-Boston is eager to welcome Motley to their institution. Their Web site boasts of his appointment, and Chancellor Jo Ann M. Gora says how excited she is to work with such an enthusiastic administrator.

Though the timing of Motley’s promotion may not be ideal, Senior Vice President for Enrollment Management and Student Affairs Philomena Mantella said the task at hand is not finding a qualified professional to fill Motley’s size 16 shoes, but instead finding a qualified presence.

“There is a force about him, it will be harder to replace the person,” said Senior Vice President Mantella.

She said that Motley was a successful administrator because of his personality and because of his leadership skills.

“I can’t imagine how many students’ lives he has impacted,” Mantella said.

Motley said through all of the years, he has met a number of students who are now coming back to him and congratulating him on the new appointment, saying to him, “We’re so happy for you — finally you’re looking out for you. Northeastern doesn’t understand what they’ll miss from you.”

But he says his main motivation is not himself.

“At the end of the day, you do it for the students. You remember that’s what it’s about.”

He also said he will miss the relationships he made along the way — especially Carmen at the coffee cart who he gets his tea from every morning. And he’ll miss being able to “just be one of the girls” and engage in great conversations regardless of gender. Over the years, the people he has come in contact with, he said, have taken great care of him.

Motley said that Rigg, who has worked with him for her 14 years at the university, was one of the main catalysts that kept him motivated throughout his career.

“Vice President Rigg has been like my agent. She has always been supportive of my growth,” he said. “She knew there was a life for me beyond vice presidencies.”

In fact, when a job came up at the University of Illinois, Chicago recently, Motley said Rigg was the first person on the phone nominating him for the position.

“She was already on the phone trying to get me there. She had negotiated a better contract than I had,” he said. “There is a sense of loss, but also an opportunity to grow. [Rigg] was very instrumental with my growth along the way.”

Rigg said she expected Motley to move on in his career, whether it was at Northeastern or another institution.

“I am delighted about Keith’s appointment. It will enable him to build on his many talents and accomplishments with the ability to develop them in a very exciting organization and as a compassionate vice chancellor. That is what a vice president should be,” Rigg said.

She expressed her hope that one of her fellow deans in Student Affairs would have filled her vacant post.

“I had certainly always hoped the Vice President [of Student Affairs] would go to Ron [Martel] or Keith [Motley]. But that won’t happen.”