People hold signs memorialising Sandy Hook Elementary School, where 26 children and adults were killed in a mass shooting on 14 December 2012Reuters

A charity formed after a shooting massacre at Sandy Hook Elementary School has lost more than $70,000 (£42,500) it raised through a marathon.

Adam Lanza shot his mother four times in the head as she slept before heading to the local school and shooting 20 students and six teachers in Newtown on 14 December 2012.

The 26.4.26 Foundation was formed in memory of the 26 victims. Marathon runners raised $103,000, (£60,700) and dedicated each mile to one of the victims.

But Ryan Graney, who co-founded the foundation, said only $30,000 had been used for the organisation's purpose.

Fellow co-founder Robbie Bruce, who was in charge of the organisation's finances, cannot be traced to account for the loss.

Bruce presented the money to the youth sports centre in Newtown in January 2013. The foundation held its first marathon in Nashville a week after the shooting. Another was held in New Hampshire last April. More than 1,400 runners raised about $22,000 for the foundation.

Graney said she noticed something was wrong last spring, when she discovered suspicious charges to the foundation's PayPal account.

"I saw there was $1,200 billed for paddle boards," she said. "I went on (Bruce's) Instagram page, and he had posted a picture of a paddle board in the back of his truck."

Graney said she confronted Bruce and he promised to meet her and go over the organisation's finances. She said he never showed up and then cut off contact with her in September.

She has now filed complaints with the FBI and Tennessee attorney general's office.

Graney said the foundation, registered as a nonprofit corporation in Tennessee, had virtually no overheads or expenses that would justify not giving the vast majority of the proceeds to the people of Newtown.

"I am in tears, sick about this," she said.

When his apartment on the southern outskirts of Nashville was visited on Friday, no one answered the door.

Graney added: "If I knew what was going on, I would have stopped it sooner," she said. "I feel terrible. I couldn't sit by and let this happen."

The fundraising effort was featured in Runner's World magazine and was the subject of several local news stories.