In shootings nationwide, police are finding the gunman is wearing a bulletproof vest -- and while it's an issue that has recently jumped into the spotlight, it's hardly a new problem for law enforcement.

"The bad guys have used body armor going way back," said John Grebert, executive director of the New York State Police Chiefs Association, noting that gangsters in the 1920s and 1930s wore vests made from cotton padding.

More companies are making body armor, and there are now more places to buy it, police say. The easier-than-ever availability has drawn renewed focus after the shooters in Binghamton, N.Y., and Pittsburgh wore vests. Federal law precludes anyone convicted of a violent felony from possessing body armor.

Body armor companies do not need any special licenses, nor are they required to run background checks. The onus is on the buyer to be truthful about his past, said Nick Taylor, manager of BulletProofME, an Austin, Texas-based company.