Brandon Williams, a 2012 Freeport High School graduate who was studying biochemistry at Wheaton College in Massachusetts and had plans to attend medical school, died unexpectedly Saturday. He was 21.

Hundreds are expected to attend a memorial service in his honor at 11 a.m. Saturday at First Parish Church UCC, 40 Main St. in Freeport.

This week, family and friends expressed shock and deep sadness over the sudden passing of Mr. Williams, who was described as a strong and sweet young man with a bright future ahead of him.

“It’s unbelievable that he’s not with us anymore,” said his mother, Bonnie Myles of Freeport. “I don’t understand why it had to be him.”

Mr. Williams was home from college on Christmas break. He went out with friends early Friday and went home to his father’s house in Freeport. They ordered take-out, watched television and talked and laughed.

Daniel Williams said his son woke up Saturday morning and got a glass of water and went back to bed. He sent his son a text message to get up for work, but he never responded. He then tried to wake up his son, but he was unresponsive. The cause of death has yet to be determined.

“He was everything to me,” his father said Wednesday. “Anything we had to talk about. … we talked. He was my only child. He was it. I have no idea what happened. I have absolutely no idea.”

Mr. Williams was a senior at Wheaton College.

He lived on campus at Beard Hall. He was dedicated to the May Fellows program and was an active member of its advisory board. His father said he had a 3.8 or 3.9 grade point average.

Kate Kenny, vice president of student affairs and dean of students at Wheaton, described Mr. Williams in an email as a kind, caring, compassionate student with a heart of gold and a great sense of humor.

“He worked very hard in all his classes and excelled in many areas, especially in the sciences,” Kenny wrote in the email.

“He had aspirations to be a doctor, and one of his faculty shared that he was taking classes in religion so he could understand better the needs of his future patients and their faith traditions. That’s the kind of guy Brandon was – loving, caring and well known to many on campus.”

Mr. Williams was published in the Wheaton Journal of Neurobiology Research on Nov. 18. He participated in the Wheaton Chorale and Chamber singers, and recently included pipe organ lessons in his study curriculum.

A highlight of his young life was working as a research assistant at the University of New England in Biddeford.

He was part of a team that conducted research on two types of sea lettuce that are common along the Maine coast. He believed that further research could “potentially serve an important role in disease prevention and treatment in the future,” he said in a 2015 article published by Wheaton College.

“He loved research. He loved the lab,” his mother said.

Mr. Williams worked at Corningware Corelle and More in Freeport. He worked tirelessly over the summer and on breaks from school.

“They loved him there,” his mother said, referring to his co-workers at the store.

In the days sinceMr. Williams’ passing, his family has received an outpouring of support from the community. His mother said friends and family are posting messages and sharing pictures and stories of her son on Facebook.

“If you could read the Facebook comments and messages,” his mother said. “It’s overwhelming. It’s more than I ever could have imagined. I knew he touched a lot of lives, but I never realized to this magnitude.”

His aunt, Sally Williams of Biddeford, believes he had a promising career in the medical profession ahead of him. She said his passing is a huge loss.

“I can’t reconcile how this young man, who was so gifted and talented, how he can be gone so quickly,” his aunt said.

“I don’t understand. I don’t think I ever will. He would have made an incredible physician. He would have been excellent at anything he put his mind to. He had this ability to make everyone around him feel good and feel loved.”