Alrighty, spoilers ahoy.
**SPOILERS
Shiro was a brave and loyal soldier, a talented assassin. Abbadon wanted Shiro as a general and so he sent a dark agent to Cantha as a fortune teller. She told Shiro his name will live on for a thousand years. He ignored her words, even after she told him fortune would come his way. Her words came true and he returned to her. This time, however, she told him that the emporer was going to kill him. He struck her down in rage, not knowing what she spoke was possessing him. With her dying breath, she told Shiro that the emporer was planning to kill him at the harvest ceremony. Shiro went insane and assassinated the emporer. He soon found his way into the Realm of Torment. And so, Abbadon ruined poor Shiro's life just so he would have a good general.
**end spoliers**
Now, this is what happens in the Factions cinematic:
As the emporer bows his head to recieve Dwayna's blessings, Shiro slays the emporer he was sworn to protect. The emporers soul energy is being drained and going into Shiro, making him even more powerful. Shiro kills the other guards, yet one escapes, sounding the alarm and sacrificing her life. The two kurzick and Luxon champions, Archemorus and Saint Viktor, rushed to where the emporer was slain. Even the two heroes could not defeat Shiro and soon, many soldiers lives were taken with only the two champions standing against Shiro. Vizu, a young assassin, heard fighting in the tower. She shadow-stepped behind Shiro, stabbing him in the back, crippling him and causing Shiro to drop his weopons. Archemorus and Viktor pick up his blades which they slay him with. As Shiro dies, he lets out a death wail that petrifies the forests and turns the seas to pure jade. The three heroes who bested him also perished.