How I Wrote That Song: Shawn Mendes & Camila Cabello "I Know What You Did Last Summer"

Shawn Mendes and Camila Cabello share how the idea for "I Know What You Did Last Summer" came to them at a Taylor Swift concert, and how they improvised parts of the song in the studio. Subscribe NOW to The Tonight Show Starring Jimmy Fallon: http://bit.ly/1nwT1aN Watch The Tonight Show Starring Jimmy Fallon Weeknights 11:35/10:35c Get more Jimmy Fallon: Follow Jimmy:   / jimmyfallon   Like Jimmy:   / jimmyfallon   Get more The Tonight Show Starring Jimmy Fallon: Follow The Tonight Show:   / fallontonight   Like The Tonight Show:   / fallontonight   The Tonight Show Tumblr:   / fallontonight   Get more NBC: NBC YouTube: http://bit.ly/1dM1qBH Like NBC:   / nbc   Follow NBC:   / nbc   NBC Tumblr:   / nbctv   The Tonight Show Starring Jimmy Fallon features hilarious highlights from the show including: comedy sketches, music parodies, celebrity interviews, ridiculous games, and, of course, Jimmy's Thank You Notes and hashtags! You'll also find behind the scenes videos and other great web exclusives. How I Wrote That Song: Shawn Mendes & Camila Cabello "I Know What You Did Last Summer"    / fallontonight