reporter: the shooting happened six blocks away from where a 7-year-oldl shot trick-or-treating on halloween she survived and the 15-year-old was arrested police say aguilar may have been a victim of mistaken identity. come forward and admit your wrongs because, you know what he probably would have been the one saving you instead of him being on the table. reporter: a nurse committed to helping save lives unable to save his own ron mott, nbc news, chicago. overseas tonight, hong kong is bracing for more violence after the standoff between anti-government protesters and riot police has escalated to new heights nbc s richard engel with the story and a warning. some of the images are disturbing reporter: students at a hong kong university were barricading themselves on campus, digging up the streets to slow down riot police to ir calls fr democratic reforms and more independence from china. this once gleaming city is descending