Stuff News on the Police press conference.
https://www.youtube.com/watch?v=YZp5XEn5wj0
No firearm license.
On home detention but exempt to go to work.
History of family violence, subject to search of his property in past.
Seems part of his home detention for family violence the property was searched, and no firearm there then.
Rampage was at his work site where he moved through site firing his weapon. (Seeming to target only his worksite)
Key part of investigation will be from where he acquired the shotgun, illegally.