Flowers, stuffed animals, posters, balloons and more continue to fill a make-shift memorial across the street from the Aurora, Colorado, theater where a gunman opened fire on Friday, July 20, killing 12.
(CNN) -- In a vacant lot across from the site of last week's movie theater shooting, 12 white crosses stand solemnly, their arms covered in messages of hope and the ground around them full of flowers.
For the loved ones of the 12 killed in the Aurora, Colorado, theater, the crosses have become a focal point of remembrance, a place to memorialize victims and pray for their families and friends. But for the man who built the white crosses, each just over 3 feet tall, the crosses are something more: symbols of his own survival since tragedy struck his family 16 years ago.
Greg Zanis, an electrician from Aurora, Illinois, said he has built 13,000 crosses in that time, each a memorial for a victim of an American tragedy.
He traveled to Tucson, Arizona, after the 2011 shooting of U.S. Rep. Gabrielle Giffords, ventured to Martha's Vineyard in Massachusetts after John F. Kennedy Jr. died in a 1999 plane crash there and went to Colorado after the Columbine school shooting that same year.
Zanis, a former carpenter, usually spends four hours each Sunday building crosses and said he "can do them blindfolded." Though he varies the cross design based on available lumber, he has a few basic styles, including a flat cross that can be attached to walls or fences and another one that can be staked into the ground at rural sites.
After the Aurora shooting, Zanis got calls from family members of Columbine victims who wanted to see how he was doing and thank him again for the crosses he built for them. It is those kinds of connections, Zanis said, that made him travel to Aurora last weekend.
"It is overwhelming to think about all the crosses I have put up," Zanis said. "I am doing it for the victims, but this is a public grieving. This allows the public a place to go to and have that big cry."
Zanis' voice cracked as he told CNN in a phone interview the stories of victims' families he met in Aurora and described praying with the city's mayor, Steve Hogan.
"I am having a hard time because I heard so many of these stories in person," Zanis said from Illinois, where he returned after spending a few hours in Colorado over the weekend.
Zanis said he began building crosses in 1996 after discovering his father-in-law dead from a gunshot wound to his head. Zanis described the scene in his father-in-law's office, where he found the body, as "gruesome" and difficult to discuss. The killer was sentenced to 15 years in prison.
Zanis attended support group meetings to deal with the grief but said that none of them helped much. In an effort to cope, the lifelong Christian built a white cross and displayed it at his home as a permanent memorial to his father-in-law.
Later that same year, a young boy was gunned down in Zanis' town. The victim's mother asked Zanis to build her a white cross as a way for her to remember her son. He obliged and has been building crosses ever since.
After a local newspaper quoted Zanis saying he'd build a cross for anyone grieving from loss, he began getting weekly calls from around Illinois. Now he receives around three calls a day from people all over the country asking for crosses, many of them families with victims of gun violence.
But Zanis said he believes that shooting deaths are "not about the gun" -- he carries one with him at times. "I don't think I am going to go murder somebody," he said. "We need to be able to defend ourselves."
Zanis doesn't charge for the crosses and said he doesn't accept donations for them. When he has the opportunity to deliver the crosses, he said he looks for a chance to talk and pray with families.
"When I talk to a family member, I talk to them differently than other people would -- I share my loss and that just opens them up to sharing their loss," Zanis said. "This is a perfect thing for me to do."
And for those who want to stay in touch, he said he is happy to be someone who will listen.
"I tell them that I am going to answer the phone even at night. I am going to be there for you, and while I won't always have the best answer for you, I will tell you that you are going to see them again in heaven," Zanis said. "It isn't final yet, I will say, and people relate to that."