Sufi School

So today, I'll be going to MTO Shahmaghsoudi School of Islamic Sufism, Inshallah. I am so freshly a Muslim that I still have yet to learn of the differences between denominations of Muslims. From what I've learned so far from others, Sufi is the "spiritual" aspect of Islam (using their words). I am intrigued by this idea & love the spiritual side of things. But. . . Isn't Islam itself "spiritual?" Isn't the very nature of religion about spirituality? Maybe I just don't understand what others mean when they use that term to describe Sufism.

I am quite excited to attend the school today, actually. I have no idea what to expect from the lecture we will hear. I do know, however, we will be chanting & praying. Also, everyone is encouraged to wear white. I have a white top, but I'm probably going to wear some black slacks or light color jeans.

I read something that threw up a flag in my mind in the Qur'an the other day. I read that if you kill (purposely) a fellow believer (Muslim), your punishment is Hell. It makes me think of the extremists we see on the news constantly, who are guilty of killing Muslims. . . If they claim to believe in the Qur'an, did they just kind of. . . SKIP that surah or what? This is very clearly stated. How does one misinterpret that?