with our friend, byron pitts. >> reporter: the glitz, the glamour. first lady jackie kennedy.remains timeless. now some of her signature style is up for sale. >> i've never been as excited. >> reporter: jackie's cartier tank watch hits the auction block at christie's. she received the watch from her brother-in-law to commemorate the 50-mile hike he took in palm beach. >> february 23rd, 1963. it has the time, 2:05 a.m., at the start of the hike and the end at 9:35 p.m. >> reporter: that hike, part of a trend sweeping the country at the time, a presidential challenge issued to americans nationwide. clint hill, co-author of the book mrs. kennedy and me. >> i had no athletic shoes to wear. i had no idea this was going to transpire. this hike. so i had to do the best i could. >> reporter: this isn't the first time jackie's memorabilia has been up for bidding. in march, a treasure trove of letters sold for over $126,000. the first lady herself created this painting which is being sold along with the watch. the lot is expected to fetch up to six figures. but it's hard to say how much

here's my "nightline" coanchor byron pitts. >> reporter: it's a narrative that keeps playing itself outd over again. >> hands up,shoot! >> reporter: unarmed black men fatally shot by white police officers. >> oh, i shot him, i'm sorry. >> reporter: critics say too often those officers are cleared of all wrongdoing. tulsa, oklahoma. a police officer shot and killed 40-year-old terence crutcher last year. >> she told a jury she thought he was trying to see if he had a gun in his pocket or his truck. >> reporter: she was acquitted three weeks ago, sparking protests. officer shelby's lawyer said today in a statement, she is still struggling with the ordeal of being charged with a crime for doing as her training provided and grieving the taking of another human life. >> this fits a narrative in america for many people that if you are black and male and you're dealing with a cop who's white, there's a chance you're not going to survive that. >> that's cherry picking what's happened in policing. it's not even accurate. >> reporter: former dallas police chief david brown says it doesn't tell th

. >> reporter: byron pitts. >>> first a principle is putting her money where her mouth is, challengeser students to step away from their phones. you're watching "world news now." because your carpet never stops working there's resolve carpet care. with five times more benefits than vacuuming alone... it lifts more dirt, pet hair and removes odours. because your carpet never stops working, resolve carpet care with five times benefits ♪ ♪ i can make you put your phone down ♪ >> oh, i see. >> a little erica badu for us? >> does she sing about anything other than making us put our phone down? >> very soothing. what may not be so soothing for some students is figuring out whether to take on this new challenge. a school principal is giving her students a new summer assignment. day every week. >> it could cost her big bucks, but she says it's worth every cent. here's jessie palmer. >> reporter: diana smith knows that devices and social media can wreak havoc on teens. >> i really want the kids not mindlessly grabbing for the phone but thinking about whether or not the phone is going to be the

>>> we are back now with our colleague, "nightline" co-anchor byron pitts who is sharing remarkablebook, "be the one." think about it. "be the one: six true stories of teens overcoming hardship" with hope. we'll talk to byron in just a minute but first what do you say we introduce you to one of those incredible people. to see the woman mckayla sanderson gut think is today a social worker who just bought her first home with her husband hard to envision the bumpy road this poised 23-year-old traveled to get here. one of seven children she was raed surrounded by domestic violence, drug abuse and mental illness. >> a lot of heartache growing up. just a lot of challenges in my childhood. >> reporter: at 8 she stood in horror as her mother attempted suicide in front of her though the gunshot was not fatal her and her twin sister would bounce between relatives and foster care for years and by the time she got to high school she had been to 13 different schools. she poured herself into school graduating at the top of her class while working 36 hours a week. how did you do all that. >> for m