Marvin LaFontaine, a friend of Adam Lanza’s mother, has said the Sandy Hook gunman may have launched his murder spree as an “act of revenge” after suffering years of bullying as a student at the Connecticut school.

Marvin LaFontaine said Adam Lanza, who killed 26 people at Sandy Hook Elementary School, one of the worst school shooting in America’s history, had been harboring resentment towards the Connecticut school for years.

The family friend also said mother Nancy Lanza was so angered by the school’s inability to protect Adam, she would sometimes sit in his class to make sure nobody touched him.

Marvin LaFontaine, who was also Adam Lanza’s Cub Scout leader when he was a young boy, told the New York Daily News: “I think Adam felt betrayed by the school and this was his act of revenge.”

He said he was told by Nancy Lanza that Adam was picked on at school.

Marvin LaFontaine said: “Adam was an easy target. He was quiet and he would never fight back.”

On December 14, 2012, 20-year-old Adam Lanza shot his mother then went on to spray 155 bullets at innocent children and educators during a five-minute bloody rampage that ended with 20 dead school children and 6 dead staff members before he shot and killed himself.

Adam Lanza launched Sandy Hook murder spree as an act of revenge after suffering years of bullying as a student at the Connecticut school

Marvin LaFontaine said Adam Lanza’s childhood experience of Sandy Hook centered on bullying.

The family friend said this angered Nancy Lanza, who would sometimes attend the school unannounced to act as her son’s “bodyguard”.

“Adam didn’t like her showing up,” Marvin LaFontaine said.

“She would sometimes sit in the back of the class and make sure no one would touch him.”

Nancy Lanza also moved Adam in and out of the school and sometimes home schooled him, according to the report.

At the same time, Adam Lanza’s mother was amassing an arsenal of weapons at the house, where investigators found more than 1,600 rounds of ammunition, two rifles, a BB gun, a starter’s pistol, nine knives, a 7-foot spear, a bayonet and three samurai swords.

Documents released as part of the investigation noted that Nancy Lanza may also have been facilitating her son’s fascination with weapons.

Nancy and Adam Lanza reportedly “bonded” during several sessions spent together at a shooting range.

According to the investigation, which is ongoing and may not be complete until June or later, each of the weapons used in the attack was legally licensed to Nancy Lanza.

They also found that Adam Lanza possessed articles on other shootings and a holiday card containing a check made out to him for the purchase of a firearm, authored by Nancy Lanza

Documents indicate that authorities found Nancy Lanza’s gun safe open with shotgun shells and numerous boxes of bullets.

A family friend told the Daily News that, in the months leading up to the shooting, Adam Lanza would dress up in military camouflage and target shoot in his basement with a pellet gun.

The family friend also said Adam Lanza’s dream was to become a Marine like his uncle Jim.

However, a man with mental health issues as marked as Adam Lanza’s is all but guaranteed to be turned away from serving in the armed forces.

That may have also contributed to an emotional break in the young man that led to his killing spree.

“I think that when he found out he couldn’t be a Marine because of his condition, that was the straw that broke the camel’s back,” the source told the Daily News.