Sandy Hook Parents Return to New School and 'Sacred Ground' at Site of Mass Shooting

On the chilly Friday morning of Dec. 14, 2012, Neil Heslin walked his 6-year-old son, Jesse Lewis, into Sandy Hook Elementary School, in Newtown, Connecticut.

Heslin watched as the first grader ambled down the hallway, carrying his trusty Disney Cars backpack – and hoping his class would make gingerbread houses that afternoon.

"That was the last time I saw him," Heslin, 55, told PEOPLE on Friday, looking back almost four years on the day his son died.

Just after 9:30 a.m. local time, in what would become one of the deadliest mass shootings in U.S. history, authorities say 19-year-old gunman Adam Lanza stormed Sandy Hook, killing Lewis, 19 other first graders and six educators, including Lewis' teacher, Victoria Soto, and principal Dawn Hochsprung, slain trying to protect their students.

On Friday, Heslin returned to the site of his son's death – and now the site of the new Sandy Hook Elementary School, which opened to the public the same day.

He carried Lewis' backpack.

"I brought [my son] to school with a book bag and hours later he came out of the school in a body bag," Heslin tells PEOPLE. He says he left the school that day in 2012 at 9:04 a.m. and sat in the parking lot until about 9:20 a.m., reading emails.

"I had just left the school when everything happened," he says.

'I Feel Numb'

On that terrible morning, Lewis urged nine classmates huddling in a corner to escape when the shooter's gun jammed, saving their lives, Heslin says. After Lewis yelled, "Run!" the gunman shot him in the head, Heslin says.

"He was a hero," he says.

Standing Friday to the right of the new school, on a grassy mound known as "sacred ground" – the exact spot where the students and teachers were killed – Heslin grew quiet, before saying, "I kind of have a feeling that Jesse is here with me."

"Being here is sad," he says. "It brings back memories, good and bad."

The last time Heslin visited the school was when he viewed the classroom where his son was shot.

"I was in the school right after it happened, so being here today is not as hard as that was," he says. "But it's sad. I feel numb at this point."

Walking slowly across the mound, Heslin said, "I'm trying to figure out exactly where he was that day."

He paused before adding, "There's no words for this."

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A 'Beautiful School' – and a 'Double-Edged Sword'

While touring the state-of-the-art school Friday, Heslin chatted with well-wishers and politicians such U.S. Senator Chris Murphy and Rep. Elizabeth Esty – and the courageous janitor who during the shooting called 911 and ran through the school while gunfire rang out, locking classroom doors and telling teachers and students to hide.

Heslin says he has "mixed feelings" about the new school, which sits further back on the property than the former school, which was demolished.

"I don't think a school should have been rebuilt here," says Heslin, who testified before Congress in 2013 about banning assault weapons. "I think it's sacred area and it's always going to be a sad place."

He wishes the land could have been turned into a park, with a pavilion for music, "so it could be a happy place again."

"With a school there, I feel like it just reminds people what happened there," he says.

He wishes the site included a memorial "with a stone there with all the names of the people who died."

"It could also be a place where people could go and honor the lives that were lost," he says.

But the sacred ground area bears no signs or plaques commemorating the shooting victims. "They call it 'sacred ground,' but I call it the murder site," Heslin says, "which is more blunt and gets the point across better."

Lewis' mother, Scarlett Lewis, did not attend Friday's open house because she flew to Los Angeles, where her son J.T. Lewis is receiving the Courage Award at Fox's Teen Choice Awards for founding the charity Newtown Helps Rwanda.

"I did visit the school, but didn't get beyond the grassy plot in the middle of the parking lot, our 'sacred space,' " she tells PEOPLE. "I cried for an hour."

Like Heslin, she wishes town officials would commemorate those who lost their lives in 2012.

"I think it would be a courageous and powerful learning opportunity for those coming into the school – how to honor and respect those who lost their lives, how to address and teach about grief and uncomfortable feelings," she says, "which would cultivate resilience, empathy and compassion while being mindful of what happened there."

But rebuilding the school "is part of the way people can heal from a tragedy like this – moving on, but not forgetting what happened," says Anthony Lusardi III, 34. His girlfriend, substitute teacher Lauren Russo, was killed in the shooting.

Lusardi knows not everyone feels that way: He tells PEOPLE, "I'm not a member of that community and I don't live down the street or a town away from where it happened, so I have some degrees of separation from it."

With the demolition and construction, he sees opportunity.

"Rebuilding a new school that looks nothing like the other one changes that aspect of it and makes it so that you are owning it as a community, which is a good thing," he says. "Somebody turned the old school into a horrible place, but now you get to take it back."

Heslin calls the new Sandy Hook a "beautiful school."

"I'm happy for the kids who will attend this school and for the generations of children it will educate," he says.

But he will always have his little boy in his heart.

"It's a double-edged sword," he says, "because my son was brutally murdered here."