women. how did it happen? and the mission to rescue tourists stranded in the grand canyon caverns randed 200 feet underground. announcer: this is nbc nightly news with lester holt good evening we will never know exactly how much higher the death toll would have been in yesterday s school shooting in st. louis had police not killed the attacker but today there is chilling new evidence the 19-year-old killer intended it to ba bloodbath. today, police revealing the gunman used an ar 15 style rifle to shoot his victims. a teacher and a student were both killed four others wounded. in addition, three people were injured during the chaos at central visual and orming arts high school authorities also saying the shooter, a former student, was carrying 600 rounds of ammunition■v but the most revealing evidence may be what police say they found in his car entries in a notebook that may offer a disturbing roadmap into his state of mind emilie ikeda is in st. louis tonight with