You can be charged with 2 counts of attempted 2nd degree murder or a lesser included offense.
According to La. R.S. 14:30(A)(3) first degree murder is when the killer has the specific intent to kill more than 1 person. This does not apply to your friend because, according to the facts you're presenting, he didn't intend to kill both of the people. If s/he has been charged with attempted 1st degree murder, there is likely a factor which you have not disclosed, or something you don't know, or the District Attorney's office has charged them using the doctrine of transferred intent.
Transferred intent basically means you mean to kill A and B, you successfully shoot A. In the process of attempting to shoot B, you miss B, but shoot C. In this circumstance, you have successfully attempted to murder two people, A and B, or A and B -> (transferred intent)-> C. A lawyer will have to explain this to you more clearly.
Alternatively, your friend can be charged with 2 counts of attempted 2nd degree murder. 2nd Degree murder is still intentional killing, but it carries the addition element of the offender must have been engaged in an enumerated felony. Manslaughter is possible as well if there was a heat of blood circumstance. Really, you should consult an attorney.
Noting the suspect's prior trouble with the law is irrelevant, unless this killing was in connection with any of those crimes.
If your friend has been diagnosed bipolar, he will have to show that at the time the incident took place the defendant didn't understand the difference between right and wrong. This is called the M'Naughten test. The problem is that someone who is bi-polar usually understands the difference between right and wrong. The burden rests with the defendant in order to prove they were insane at the time of the incident.
A stronger argument may be made that the defendant is not competent to stand trial and cannot aid in his defense. This will slow the process while a determination of competency is made by the court.
Given the severity and particularity of the offense, I strongly recommend you consult and attorney.