The post I was replying to was the first time I had heard anything about a vest. This could be a case of runaway speculation and gossip.
The report was based on a police report heard here, describing the shooter as wearing *a black vest with ammunition clips* which could also have been the black leather jacket reported by some witnesses. A CBS report also described a possible vest, as follows:
The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives believe the gunman, described as a young Asian male, used two handguns in the shootings before taking his own life, sources tell CBS News. One official added that the gunman was "heavily armed and wearing a vest."
Alternately, one of the early responding cops to the first 07:15 shooting at West Ambler Johnston residence hall where the first two victims were killed may have been wearing a bulletproof *raid vest* or tactical vest and was then mistaken for the shooter.
Too soon to tell.
I wonder if the FBI is investigating link between the shooter and the Northern Virginia jihadi group that practiced by playing paintball?
http://www.jihadwatch.org/archives/003308.php