Lamar Odom "is beside himself" over best friend Jamie Sangouthai's death at 37 from a reported heroin overdose Sunday, RadarOnline.com has learned.
An insider close to Khloe Kardashian's ex told US Weekly Sangouthai's death marked "the worst tragedy," while a separate source told the magazine that "Lamar is going to take this really hard," as he and Sangouthai "were best friends, like brothers.
"This is so sad."
As RadarOnline.com previously reported, Khloe -- who was vocal about Sangouthai being a bad influence on Odom, on their old reality show Khloe & Lamar -- tweeted, "When does it stop? RIP Jamie Sangouthai."
She later posted an image of a crying woman with the caption, "Life doesn't get easier but I promise you that life will make you stronger."
Khloe confidante Malika Haqq also paid memorial to Sangouthai on her Instagram page, writing, "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."
Sangouthai had been silent on social media for some time, having not posted on his Instagram page in nearly three months.
Sangouthai, according to online reports, was pronounced dead Sunday at a Los Angeles hospital.