The fiancé of a New Jersey high school principal who died while donating bone marrow to a French teen he had never met filed a lawsuit on Monday that names the hospital where the procedure was performed. Derrick Nelson, who was also an officer in the Army Reserve for more than 20 years, died in April after he fell into a coma at Hackensack University Medical Center.

The 44-year-old who was survived by his fiance Sheronda Braker as well as their 6-year-old daughter, had matched with the teen through the donor network Be the Match.

“If it’s just a little bit of pain for a little bit of time that can give someone years of joy, it’s all worth it,” Nelson had told the Westfield High School student newspaper.

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Ahead of his procedure, Nelson had told media outlets that he had sleep apnea, and was also the carrier of the sickle cell trait. He had said that doctors decided to proceed with the bone marrow procedure using a local anesthetic.

But Braker’s lawsuit alleges that an anesthesiologist committed medical malpractice during the procedure, and as a result, Nelson suffered fatal brain damage, according to MyCentralJersey.com.

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“After the procedure he did, he couldn’t speak and was lying in the bed,” Willie Nelson, the man’s father, had told NJ.com at the time. “His eyes were open, and he realized who we were. But he couldn’t move. He never spoke again.”

Nelson died on April 8. The couple had planned a June 29 wedding ceremony, according to MyCentralJersey.com.

The Associated Press contributed to this report.