Washington, Sept 18, 2019 (AFP) -A man shot and killed three teenagers on his front lawn in the southern US state of Georgia during an alleged robbery attempt, police said, raising the prospect of no charges if the shooter is found to have acted in self-defence.Georgia is one of 27 US states with so-called "stand your ground" laws, which establish a right to use lethal force to defend oneself or others against a perceived threat.Police in Conyers, a small town near Atlanta, said the shooting occurred Monday when the three youths, one of whom was 15 and the other two 16, approached a house before dawn."To this point, the investigation has revealed that the three now deceased individuals had their faces covered as they approached the residence and attempted to rob three individuals in the front yard," a Rockdale County police spokesman said in a statement."One of the attempted robbery suspects brandished a handgun and fired shots at the residents before one of the intended robbery victims returned fire," the spokesman, Lee Thomas, said."The victims of the attempted robbery were all uninjured, but the three attempted robbery suspects were all shot during the exchange of gunfire and succumbed to their injuries, one on scene and two at a local hospital after being transported." Thomas told AFP no charges have been filed and that the investigation is "still active."Rockdale County Sheriff Eric Levett was quoted by local media as saying the case could fall under the state's laws on self-defense, which permit the use of lethal force even if other options, such as running or hiding, are available.The right to self-defense is a key argument advanced for gun ownership by the National Rifle Association, a major political force in the United States.The so-called "stand your ground" laws have been at the center of other controversies, including the 2012 shooting death in Florida of Trayvon Martin.An unarmed black 17-year-old, Martin was killed in a confrontation with an armed neighborhood watch guard, George Zimmerman, who was acquitted of second degree murder after employing a self-defense argument.Outrage over the verdict helped fuel a backlash that ultimately led to the "Black Lives Matter" movement.In the Conyers, Georgia case, two of the youths who were killed were African American and the third was Hispanic.