A handgun that belonged to a family member was found at the scene, and police said the death appeared to be a suicide.
Vincent was reported missing after disappearing Aug. 27, telling family members he was going to the Glendora library to study.
His uncle, Bill Cooper, told the San Gabriel Valley Tribune that Vincent was "genuinely a nice, good, caring kid.
"We spent a lot of time hiking together and stuff," he said. "I'm going to miss him for the rest of my life."
A cousin spotted the body first. Police said it appeared Vincent had been dead about two weeks.