Investigators at Hopkins reviewed 11 years of data and found that 30 percent of hospital shootings occurred in emergency rooms. Nearly 50 percent of those shootings involved a security officer's gun - either stolen or used by a security.
The study found that most perpetrators had a personal relationship with victims.
The report was published Sept. 18 in the online version of the Annals of Emergency Medicine.
Common motives for shootings were grudge or revenge, suicide. and euthanizing an ill relative.
The report is published two years after a shooting at Hopkins. In that shooting, Paul Warren Pardus shot a doctor and then killed his ill mother and himself.
The Hopkins researchers said that specialized training for law enforcement and security personnel, such as proper securing of firearms, may prove a more effective deterrent to future shootings t han technologies, such as magnetometers.
They said no hospital is immune to a shooting.