The mother of an openly gay Alabama teenager who died by suicide in April, after allegedly being bullied over his sexuality, is calling for an investigation into his death.

Nigel Shelby was a 15-year-old freshman at Huntsville High School in Huntsville, Alabama. Camika Shelby, his mother, says school officials told Nigel "that being gay was a choice."

Nigel Shelby died by suicide after being bullied for being gay. GoFundMe

“After my son passed, I learned that he had several discussions about homosexuality with school administrators and was told that being gay was a choice," Shelby said in a statement released by her attorneys Monday. "I was never contacted by the school and informed that my son was struggling with his sexual identity and regularly having discussions with a school administrator."

Shelby told NBC News other students witnessed the conversations administrators had with her son.

Several hours after Nigel died on April 18, his mother claims she was contacted by a school administrator who told her to look for a suicide note in his backpack.

"People at his school knew that he planned to take his own life," Shelby said. "I need to find out who knew and why nobody told me until after he died.”

Shelby has retained civil rights attorneys Benjamin Crump and Jasmine Rand, who are investigating the circumstances involving Nigel's death, including the bullying he allegedly experienced at his high school.

“As civil rights leaders, we have a duty to ensure all of our children are safe in school and treated with equality, and that educators address and guide children struggling with gender and racial identity issues in a positive and loving way that benefits the growth of the child," Crump and Rand said in a joint statement.

The Huntsville City Schools District said neither it nor Huntsville High School received any complaints of bullying and harassment of Nigel prior to his death. A spokesman for the school district said it "will work with Shelby and her attorneys to answer questions they may have and to correct any misunderstandings or misinformation, to the extent possible."

"The administrators and counselors of Huntsville High School had a close relationship with Nigel during his time at the school," spokesman Keith Ward told NBC News on Wednesday. "They worked with Nigel to ensure that he felt at home at Huntsville High."

Ward said the school staff were "absolutely devastated by Nigel’s passing and tried to do everything in their power to support Ms. Shelby during that difficult time."

Shelby said any claim that the school had a close relationship with her is untrue.

Her attorneys contend it was not the school's place to have so many conversations with Nigel about his sexual identity without the presence of his mother or mental health professionals.

"Clearly they did not do what is right by Nigel because he is not here today," Rand told NBC News on Wednesday.

Shelby told NBC News that in recent years Nigel struggled with depression and had told her his sexuality made him a target of bullies.

Lesbian, gay and bisexual youth are almost five times as likely to have attempted suicide than heterosexual youth, according to The Trevor Project, which provides crisis- and suicide-prevention services to LGBTQ youth.

If you or someone you know is in crisis, call the National Suicide Prevention Lifeline at 800-273-8255, text HOME to 741741 or visit SpeakingOfSuicide.com/resources for additional resources.

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