Khloe Kardashian is mourning the loss of Lamar Odom's best friend.

The 'Keeping Up with the Kardashians' star is devastated after Jamie Sangouthai - who was one of the basketball star's best men at their 2009 wedding - passed away yesterday (14.06.15) at the age of just 37 following a reported heroin overdose.

Alongside a broken heart emoji, she tweeted yesterday afternoon: ''When does it stop? RIP Jamie Sangouthai.''

Khloe's estranged husband is said to be ''beside himself'' by the loss of his former school friend and occasional business partner.

A source told Us Weekly magazine: ''Lamar is beside himself. This is the worst tragedy.''

Another source added: ''This is so sad. They were best friends, like brothers. Lamar is going to take this really hard.''

While Lamar has yet to comment on the news, 30-year-old Khloe's close friend Malika Haqq is also saddened by their pal's passing.

Alongside a photo of herself, Jamie, Khloe and Lamar, she wrote on Instagram: ''Thru good and bad times life shows us every spirit matters and leaves a print on the hearts of others after they have passed... RIP Jamie Sangouthai #GodHelpUsAll.(sic)

Jamie was rushed to a Los Angeles hospital for treatment after emergency services were called on Sunday, but died at the medical facility.