LOS ANGELES, March 1 (Xinhua) -- A billboard near Interstate 15 crossing downtown Las Vegas was vandalized as a shocking sign against gun violence early Thursday morning. An activist art group claimed responsibility for this prank.

The billboard was designed for Battlefield Vegas, a shooting range in the city of the U.S. state of Nevada, showing a machine gun and an advertising sentence "Shoot a 50 Caliber Only $29 (29 U.S. dollars)." On Thursday morning, the words were found to have been changed to "Shoot a School Kid Only $29" while over the phone number for Battlefield Vegas was also pasted "Defend Lives Reform Laws."

INDECLINE, an American activist art group composed of graffiti writers, filmmakers, photographers, claimed the vandalism Thursday and provided a video online that shows two members of the group making changes to the sign at night.

Local ABC 13 news channel quoted a message from INDECLINE as saying that it did it because of "America's longstanding obsession with gun culture and our government's inability to honor the victims of mass shootings by distancing themselves from the homicidal policies of the NRA (the National Rifle Association)."

In the message, INDECLINE also said it is "calling on all political parties to immediately work towards a legislative resolution that aims to protect citizens and reform inadequate gun laws that are currently placing value on assault weapons over that of human life."

The billboard was covered up Thursday morning.

The wild protest happened just two weeks after a mass shooting at Marjory Stoneman Douglas High School in Parkland of Florida that killed 17 people on Feb. 14.