The Oakland County Medical Examiner’s Office ruled this week that the death of Cranbrook student Caleb Lei was due to natural causes, police said.

Lei, whose family resides in Ann Arbor, was born in Livonia but grew up in Troy, where he attended Boulan Park Middle School, according to his obituary on Desmond Funeral Home's website.

The ruling formally concludes the joint police-coroner investigation into the 15-year-old's death on the Cranbrook campus Oct. 5, Lt. Terry McDonnell said in a prepared statement. Further details were not released.

Officers responded to a medical emergency call at one of the residential facilities for boys at about 5 a.m. and found an unconscious Lei in the hallway, police reports said. Attempts to revive him with CPR were unsuccessful, Chief Rick Matott said.

Investigators found no signs of foul play and suspected natural causes in Lei's death; however, they launched the investigation with the medical examiner's office per department policy.

Lei's death lead to an outpouring of online tributes, comments and memorials that, in general, described him as a thoughtful young man, a good friend, and talented musician. Lei was a member of Cranbrook's String Quartet that won first place at the Detroit Chamber Winds and Strings Chamber Competition at Kirk in the Hills in February.

"Sending much love to the Lei family. Remembering Caleb, such a wonderful young ornithologist, kind and gentle listener, wise older mentor . . . We will never forget him," Amy Rust Higgins wrote recently on a Facebook Page established in Lei's honor.

That same Facebook page promotes a Caleb Lei Memorial Concert at 8 p.m. Sunday, Dec. 16 at Oakland University. The event features the Tuesday Musicale of Detroit, Student League Members — of which Lei was a member — performing music by Debussy, Beethoven, Chopin, and others. Donations will be accepted at the door and will benefit an award to a young violinist or pianist in the Student League. Contact Velda Kelly at 248-474-8930 or veldaviolin@gmail.com.