Ummm .... shouldn't an arrest be immiment?

Maybe I've seen too many police procedural shows like CSI, but when a gun used to MURDER SOMEONE shows up in the hands of the dumb-ass teenage shooter/would-be gang lord who tried to murder a student at Woodruff High School, shouldn't that mean the teen shooter ends up arrested and charged with the murder? Maybe the rules on Peoria are different. And someone please explain to me why the HELL it took NINE FUCKING YEARS for ANY word to leak out that the murderer used the same gun that was used to shoot up Woodruff High School.