New disturbing details in the Jonathan Martin case ... we've learned he was arrested with a cache of weapons including a loaded shotgun, knife and an ax -- and had been threatening classmates for years.
TMZ Sports has obtained court documents filed after Martin was taken into custody on Feb. 23 after posting a cryptic photo on Instagram threatening old high school classmates and former NFL teammates.
Officials say they found Martin after getting a call about a "suicidal male with a gun" at a hospital in Glendale, CA.