Joy Reid leads this episode of The ReidOut with the deadly school shooting that just took place in Michigan, as we mark five years since a gunman took the lives of 14 high school students and three staff members in Parkland, Florida. Fred Guttenberg, father of Jaime Guttenberg, who was killed in the Parkland shooting, and author of "Find The Helpers: What 9/11 and Parkland Taught Me About Recovery, Purpose, and Hope," joins The ReidOut as we remember this tragedy. Plus, former South Carolina Gov. Nikki Haley steps into the ring to challenge Donald Trump as Mike Pence says he plans to fight the special counsel's subpoena. Our experts analyze both developments. Finally, twitter whistleblower Anika Navaroli joins Joy to tell us what she learned at House Republicans' hearing on alleged liberal bias on social media. All this and more in this edition of The ReidOut on MSNBC.