hailey steinfeld's catchy song nationwide fight to stop bullying. the campaign to choose kindness. i love my i love mile no, i don't need anybody else >> but first -- the "nightline" >>> number 1 in just 60 se we begin with an investigation into the potential dangers of accidentally leaving your car running with some keyless ignition systems. they've played a role in a number of deaths by carbon monoxide, which in some cases can kill you after a handful of breaths. tonight abc's alex perez finds out if your own car can put you at risk and how to stay safe. >> we're going to go down, we're going to mask up on the floor. >> reporter: firefighters armed with masks and safety gear. they approach cautiously knowing this garage is filled with deadly concentrations of carbon monoxide from the exhaust of this car left running. it's a frightening demonstration, but in real life it can have tragic results. investigators have confirmed 12 deaths since 2009 that are linked to carbon monoxide poisoning from cars with keyless ignition that had been accidentally left running. recently among them

hailey steinfeld's catchy song becoming an anthem for a nationwide fight to stop bullying. the campaign to choose kindness. i love mile else >> but first -- the "nightline" 5. >>> number 1 in just 60 seco it is time to deal with skyrocketing out-of-pocket costs. head of a pharmaceutical company raised the price of a life-saving drug overnight by 5,000%. i'm announcing a detailed plan to crack down on these abuses. commentator: he may be lowering it after hillary clinton blasted him out of the water. her plan would limit the out-of-pocket costs that consumers have to pay. clinton: nobody in america should have to choose between buying the medicine they need and paying their rent. i'm hillary clinton, >>> good evening. we begin with an investigation into the potential dangers of accidentally leaving your car running with some keyless ignition systems. they've played a role in a number of deaths by carbon monoxide, which in some cases can kill you after a handful of breaths. tonight abc's alex perez finds out if your own car can put you at risk and how to stay safe. >> we're g

hailey steinfeld's catchy song becoming an anthem for a nationwide fight to stop bullying.