As I recall she put four bullets in his chest. While not instantly lethal, it's hard for a person not to bleed out from that in a matter of minutes. In a way that's even more cold than just finishing him off with a headshot. She killed him the slow way...or would have if it weren't for the kevlar.
Speaking of: it wasn't a full vest, just a kevlar plate slipped into the side of his leather jacket and as we saw, it only caught two of the slugs. If Agent 33 hadn't come along there's a good chance he would have bled out. People appear to be under the misapprehension that a person can't be badly wounded when wearing a bulletproof vest. Short of a full suit of body-armour that's just not the case.
Even in full tac gear there are soft spots between the plates, around the joints and other regions that the wearing will need to flexibility. At best a vest protects the vital organs as much as is *practical*, as in not so much that the wearing can't operate effectively.
Same with any safety gear really and speaking as someone who at one point in his life went to work with a hardhat, high-vis vest, fall harness and steel toecapped boots, I can tell you that nothing makes you invulnerable. It'a all about reducing (not eliminating) risk and minimising injury in the case of an accident...and keeping the bloody health and safety inspectors off your back.
In Ward's case, he a covert operative/wetwork specialist who needs to move fast, light and blend in with a civilian crowd. Under those parameters, a few kevlar plates sewn into a jacket lining is as much protection as he can get away with. Anything more would be a hindrance.
