11:01 AM PT -- Fuller's brother called 911 after the RB collapsed to the ground and told the operator it appeared he was having a seizure.
The caller said Fuller had "passed out" -- though it's unclear if he was conscious at that point.
CJ's brother and other family members desperately tried to help Fuller -- following the operator's instructions -- and begged for an ambulance to be sent over quickly.
8:20 AM PT -- A source extremely close to Fuller tells us the football star had gone to physical therapy to rehab his knee in the hours before his death .