President Snow reminds Katniss that it was President Coin, not President Snow, who put off the explosives that murdered her sister. As a result, a riot breaks out, and President Snow is discovered dead, either from choking on his own blood or being crushed by the throng. This all happens during the 75th Hunger Games. Now, this doesn't necessarily mean that President Snow is immortal - he could have died from natural causes or been killed by another contestant. But since he was delayed by his death, Katniss has an extra day to think about District 12 and their situation. This gives her time to come up with an idea that may help them both. In the final chapter of Mockingjay - Part 2, we find out what happened after President Snow's death. Knowing that Katniss has one more day before she has to make a choice for herself, Peeta goes back in time and saves her life. This allows Katniss to live long enough to see Capitol president Coin take office instead of president Snow. In addition, Peeta also prevents Katniss from killing herself by shooting her with a stun bullet, giving them both a chance to change their minds. So President Snow did die near the end of Mockingjay - Part 2, but not before saving Katniss' life.