Earlier I was questioning whether the Shooter indeed had body armor. And I came across this article, and this picture.
I can't tell what all the items are, but the article lists them as ballistic helmet, goggles, a gas mask, a ballistic vest, ballistic leggings, along with throat and groin protectors and black tactical gloves, and in the top left I can see the Blackhawk fishing vest. Another photo in the article shows a police shield.
So our shooter was well protected as far as body armor goes.
The only question now is the quality and effectiveness of the armor he chose, just looking at the photos it looks rather bulky and it certainly likely that the armor could have been reinforced with ballistic metal plates.
These metal plates not only help to keep bullets from penetrating the armor, but also to spread out the impact force of the bullet over the entire width of the plate.
Without the plates which never cover the armor completely, handgun rounds can still be effective in stopping a person wearing body armor.
This link is to a web site that is always testing bullet ballistics and such, in this link they are testing "shootpacks" (18"x18"), this is the material used for bullet proof vest. The informal results show that although the "shootpacks" will not allow a bullet to penetrate, that significant damage can still be achieved.