A commission behind a memorial for teenage lynching victim Emmett Till in Mississippi was forced to get a new sign with a glass bulletproof front and add cameras and alarms after previous markers were riddled with bullet holes.

It’s one of numerous monuments to U.S. civil rights figures or events around the country that have been attacked by vandals through the years, forcing organizations and elected officials to spend hundreds of thousands of dollars to repair or replace the monuments and equip them with surveillance. There’s no movement to pass federal protections for such memorials, and advocates of the sites say their only recourse has been to rely on local and state vandalism and hate crime laws to prosecute suspects.

“It happens so much that I can’t get angry because I’m not surprised,” said Maria Varela, a Mississippi civil rights organizer and photographer with a Student Nonviolent Coordinating Committee in the 1960s. “But this tells me the people who are doing this are still so scared.”

The need for protection for such memorials came into focus again this month after security cameras captured white nationalists trying to film in front of the new sign that describes how the body of Till, a black 14-year-old from Chicago, was pulled from the Tallahatchie River in Mississippi. A man in the security video said the memorial represents the civil rights movement for black people. He then asks, “Where are all the white people?” One person carried a white flag with a large cross, a symbol associated with the League of the South — called a neo-Confederate hate group by the Southern Poverty Law Center. After a security alarm went off, the group ran away without doing any damage.

The cameras and alarms are part of an updated security system that accompanies the 500-pound steel sign after three previous markers were vandalized, including two that were left riddled with bullet holes.

“Without a doubt, those cameras have helped deter potential vandalism,” said Patrick Weems, executive director of the Emmett Till Memorial Commission.

Till was visiting family members in Money, Mississippi, in August 1955 when a white woman at a store falsely accused him of whistling at her. The woman’s husband and another man were charged with kidnapping, beating and fatally shooting the teen. An all-white jury acquitted the men.

The killing and photos of Till’s mutilated body at his funeral shocked the nation and galvanized the civil rights movement.

Weems said memorial preservation and fundraising should be done with potential vandalism in mind. The new, donated sign cost around $10,000, he said. Plus, the commission has paid $1,000 for security cameras, and an estimated $250,000 is being spent on a smartphone app that will allow people to navigate sites related to Till’s killing and to report vandalism, he said.

At other memorials, updated security measures have helped authorities locate suspects. In September, a 65-year-old woman was arrested after police say she defaced a memorial in Glendale, California, dedicated to Korean women forced into sex slavery during World War II. Police said surveillance footage showed her using a marker to scribble on the monument. She’s suspected of defacing the monument several times before and of writing racist graffiti on area buildings.

“The defacement opened up the wounds of the victims as if to say your pain doesn’t matter,” Phyllis Kim of the Korean American Forum of California said. “But the community came together and denounced it.”

Derek H. Alderman, a University of Tennessee geography professor, said such vandalism is “an attack on memory.”

“These places are more than just monuments and memorials. They are claims to the past,” Alderman said.

Those claims involve marginalized groups pressing to be remembered while white nationalists and racists refuse to acknowledge those struggles, he said.

“When a memorial to victims of brutality and violence is met with brutality and violence, it strikes a chilling nerve and shows how far we have to go,” Alderman added.

Jose Vega, deputy director for Oklahomans for Equality in Tulsa, said the advocacy group’s offices are a frequent target of vandalism. In July, surveillance video caught a man spray-painting the word “abomination” over a mural dedicated to gay playwright Lynn Riggs.

“We knew this was going to happen and were mentally prepared,” Vega said.

Jeremy Yamin, associate vice president for the Boston-based Combined Jewish Philanthropies, which maintains surveillance of the New England Holocaust Memorial, said such attacks appear to be on the rise.

After 20 years with no vandalism, the Holocaust Memorial was hit twice in 2017, he said. His group spent $70,000 on repairs and $75,000 on security cameras.

Yamin said the group is preparing to put up a sign that says: This memorial is monitored.

“We hope that will be a deterrent,” he said.