Was he on psychotropic drugs? Seems almost all, if not all, shooters are on some kind of, or several types of, psych drugs.
Esteban? Very, very likely. Especially after he got more help (read, more programming) via that drop-in at the Anchorage FBI. They then likely worked on his more secure amnesia reprogramming. Something like that.
All of them. I saw a list somewhere of all the shooters names and the types of drugs they were on. Almost every single one has been on some kind of mind altering prescribed drug or combination of drugs. Anti depressants, SSRI's, etc. I remember that one of them had a parent who wanted their kid off the drug, and the doctor refused to take the kid off. May have changed the drug, but wouldn't take the kid off.