Assuming your friend was arrested, he was most likely charged with "aggravated battery with a deadly weapon", punishable up to 15 years. The Florida Sentencing Guidelines will score this offense as follows: 56 points for the aggravated battery, plus 40 points for severe victim injury, subtract 28 points, multiply by .75; this computation equals 51, which is the lowest number of months in prison your friend could serve, with a maximum of 15 years in prison. This computation also assumes that your friend has no prior criminal history.
Your friend must contact an attorney right away to discuss defenses and sentencing options. Justifiable use of deadly force might apply under the circumstances. An attorney will also discuss possible sentencing alternatives via a departure from the guidelines based on youthful offender or willing participant/victim if applicable. This case is extremely serious, and your friend should not discuss the facts of this case with anyone until he has consulted with an attorney.
Your friend should immediately hire an attorney. Your friend should refrain from discussing the facts of the case with anyone besides his lawyer, nor should he make any posts on the internet about it.
Your friend may have a valid self-defense argument. Additionally, an attorney could move to have the charges dismissed under the "Stand Your Ground" law in Florida.
It is true he could be charged with aggravated battery with a deadly weapon or causing great bodily harm. An aggressive prosecutor may even try to argue it was attempted manslaughter or attempted murder. Without knowing all the facts it is impossible to say for certain what the exact charges will be or what your friend should do. But one thing for certain is he should get an attorney because it does sound like a possible self defense case, and again, a possible motion to dismiss based on Stand Your Ground. Your friend could be in serious trouble so he needs to take this seriously and he needs a serious attorney.