NOTHING is simple when it comes to the gun issue, in part because nothing is simple when it comes to guns. Types, makes, models vary considerably, and so do laws governing them. That's why discussions about laws regulating or controlling guns get complicated (that, and the NRA's effectiveness at keeping these issues cloudy). When we're talking about the kind of gun that killed Sgt. Liczbinski, it gets even more so. But arguing about the need for common-sense gun laws must include a better understanding of the range of guns out there, and the kind of harm they do. Here's the lowdown on the SKS:

What is it?
Like poison pet food and toxic toys, the SKS semi-automatic assault rifle is another deadly gift from China. This weapon was designed by a Soviet arms designer named Simonov (which contributes one "S" in SKS) for use on the front against Germany. China got the license to the design and started manufacturing them in great numbers.

How does it work?
It is a gas-fired, semi-automatic gun, which means it fires one round and instantly loads the next round with each pull of the trigger. Automatic weapons keep firing as long as the trigger is depressed. Semi-automatics fire more slowly than automatics, but not by much. The SKS is powerful enough to rip through a bulletproof vest.

How easy is it to get one?
In Pennsylvania, as easy as buying a handgun: Walk in, pass an instant background check, walk out with an SKS.

Wasn't this gun banned at one point?
The U.S. — in a rare moment of sanity — outlawed assault weapons in 1994. This ban expired, though, in 2004 and it has not been renewed. Even so, this ban was too limited. The SKS was not covered because it didn't contain enough of the precise list of features that applied to "assault weapons," like grenade launchers and bayonet mounts. (The gun used by the D.C. sniper wouldn't have been covered under the ban, either.) But many maintain that a gun designed for military use on the battlefield should be considered an assault weapon. The city's ban on assault weapons that Mayor Nutter signed last month, which was not legal, would have included the SKS.

Didn't Philadelphia once have a law banning assault weapons?
Yes, in 1993; Harrisburg lawmakers killed it in 1994, saying cities can't pass laws that preempt the state's.

How much of a problem are these guns? Have they killed other police?
Well, that would be useful information to know, wouldn't it? But the public is restricted from gun-trace information after 2000, thanks to the Tiahrt amendment that limits the ability of the ATF to share gun-trace data. According to the Violence Policy Center, though, 11,591 SKS rifles were traced to crime scenes from 1995 to 2000.

Anecdotally, the SKS is a big problem for police. In fact, during the Clinton administration, there was so much concern on the streets about this gun that a law was passed to exclude these from importation from China. President Bush went on to authorize those manufactured from Yugoslavia.

According to one ATF report, the SKS is the No. 1 gun for offenders 17 and under.

Is there any sane approach to assault weapons out there?
California is cited as a state with a strong assault-weapons ban that addressed the weaknesses in the now-expired federal ban. That's a ban worth fighting for.