“This was a deeply disturbed kid,” a family insider told the Daily News. “He certainly had major issues. He was subject to outbursts from what I recall.”…

A “longtime” family friend said Lanza had a condition “where he couldn’t feel pain.”

“A few years ago when he was on the baseball team, everyone had to be careful that he didn’t fall because he could get hurt and not feel it,” said the friend. “Adam had a lot of mental problems.”…

He was also seen as an odd figure at Newtown High School.

Even before that, Lanza walked the halls of his middle school carrying a black briefcase while most students lugged their belongings in backpacks. “That stuck out,” said Tim Lalli, 20, who graduated with Lanza in 2010. “It was different.”