Jamie Sangouthai, the best friend of former NBA player and reality star Lamar Odom, has died of an apparent heroin overdose. He was 37.

According to TMZ, Sangouthai died Sunday at a Los Angeles hospital, where he was taken after someone called 911.

Sangouthai, who played basketball with Odom in high school, made numerous appearances on Khloe & Lamar, Odom's reality series with estranged wife Khloe Kardashian. Sangouthai also served as Odom's best man at his wedding.

"When does it stop? RIP Jamie Sangouthai," Kardashian tweeted Sunday.

A source told Us Weekly that Odom, who has struggled with his own substance abuse problems, is "beside himself" at the news.

"They were best friends, like brothers," another source told the site. "Lamar is going to take this really hard."