NEWTOWN, Conn. (CBSNewYork/AP) — Newtown held a moment of silence and flags were flying at half-staff across Connecticut to mark the fourth anniversary of the Sandy Hook Elementary School shooting.

Complete Coverage: Newtown School Shooting

It was Dec. 14, 2012, when a troubled 20-year-old gunman shot his way into the Connecticut schoolhouse and killed 20 children and six educators. Adam Lanza fatally shot his mother before driving to the school, and then killed himself after the rampage.

Link: Learn More About The Victims

The town typically does not hold an official memorial event on the anniversary of the tragedy, but prayer services are planned for Wednesday and a counseling center will be open for extended hours.

First Selectman Pat Llodra asked town employees to refrain from doing any work, including answering phones, between 9:30 a.m. and 9:45 a.m. to mark the time when the shootings took place.

In Memoriam: The Victims Of The Sandy Hook Elementary School Shooting

In the years since the shooting, Newtown parents who lost children in the tragedy have stood together in their effort to heighten awareness about mental illness.

Mark Barden is among those who joined in a unified effort to craft the Mental Health Reform Act, which was signed into law Tuesday.

Photos: Shooting At Sandy Hook Elementary School In Newtown, Conn.

Barden believes the tragedy could have been avoided had Lanza’s parents come to terms with their son’s mental health deterioration.

“We are working hard to prevent acts of violence before they happen by training people with the tools to identify somebody who may be on their way to self harm, or harming someone else,” Barden said.

Barden said he and his family struggle daily to cope with the loss of his son, first-grader Daniel Barden.

“To look at the empty chair across the table and have to recognize the fact that our sweet little Daniel is gone, he is gone forever, and he is gone because of someone else’s choice, and that’s something will have to always live with,” Barden said.

Nicole Hockley , who lost her son, Dylan, said she has yet to grieve.

“I’m not ready yet,” Hockley told WCBS 880’s Peter Haskell. “I’m still on a path, and I will start grieving in my own time when I’m ready, a little bit at a time.”

Hockley has been a tireless advocate to prevent gun violence, and has made several trips to Congress for the effort.

“My way of dealing with grief is to stay very busy and try to make Dylan’s death mean something by saving the lives of others,” said Hockley. “In my opinion, D.C. is broken.”

(TM and © Copyright 2016 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2016 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)