The father of a first-grader killed in the 2012 massacre at Sandy Hook Elementary School was discovered dead in an apparent suicide Monday morning at a town hall in Connecticut, police said.

Authorities said that the body of Jeremy Richman, 49, was found at about 7am at Edmond Town Hall in Newtown, a city scarred by a school shooting that left 20 students and six staff members dead, including Richman's daughter, Avielle Richman.

Lt. Aaron Bahamonde, a spokesman for the Newtown Police Department, told The Washington Post that Richman's death "puts Newtown back into the spotlight again".

"We certainly recognise the heartbreak that this is causing," he said in a phone interview. "It's a difficult situation that we're all dealing with here and it's a sad situation."

Authorities said that Richman, who founded the Avielle Foundation, a nonprofit that aims to prevent gun violence, had an office at the Edmond Town Hall.

Authorities did not release further details but said Richman's body will be transported to the state medical examiner's office for an autopsy, expected to be completed later in the day.