The facts are still emerging from the Nevada school shooting Monday, in which a 12-year-old student at Sparks Middle School allegedly shot and killed a popular math teacher and injured two male classmates before killing himself. Even the name of the shooter has still not been released.But among the facts authorities have revealed is that they believe the shooter got the Ruger 9 mm semiautomatic handgun used in the attack from his home.The boy reportedly brought the gun to school grounds and, just before classes started for the day, wounded one student, shot and killed math teacher Mike Landsberry, and wounded another student before turning the gun on himself.While it's too soon to know how the shooter was able to get access to the gun he brought from home, most underage school shooters obtain their weapons from home, a relative, or another home where they knew guns were kept.Questions are already being raised about whether any adults could be held criminally liable if they are proven to have negligently allowed the student access to the firearm.At a news conference, Sparks Deputy Police Chief Tom Miller said the local prosecutor will have to determine whether to press charges against the shooter's parents if, in fact, the gun came from their home, "but the potential is there."Other examples also point to that possibility, but they suggest that the prosecution of such cases varies widely, whether or not states have laws specifically targeting negligent parents.For its part, Nevada is one of 27 states that does have a Child Access Prevention (CAP) law. But some laws are more stringent than others.Nevada, like 12 other states, prohibits only intentional, knowing, or reckless provision of firearms to minors. Several other states impose liability if the child actually uses the firearm. Only three - Massachusetts, Minnesota, and California (plus the District of Columbia) - impose liability when a child "may" or "is likely to" gain access to a gun, even if they never do.Of these, Massachusetts is the only state that has a true "safe storage" law on the books, says Sam Hoover, a staff attorney at the Law Center to Prevent Gun Violence. The Massachusetts law requires that guns be locked at all times in the home, except when used in self-defense. In addition, all guns in Massachusetts must be kept with a locking device in place.Parents Could Face Charges in School Shooting