I saw the video, even if this man was not military trained, he did train somewhere with professionals. One doesn't have to be in the army to train like army, there are other sources. That's why it has been mentioned in the media that he had been planning these attacks for over 2/3 years. Probably he was training himself with the weapons he ultimately used. He probably was also training with explosive. Explosives were found by the police.
What made me shocked is that he went back to the main prayer hall few times and sprayed the bullets in same directions more than once to make sure no one survives. That shows his sick mind.