Washington, September 25 (RHC)-- A study by the Federal Bureau of Investigation (FBI) shows the number of mass shootings in the U.S. has increased significantly in recent years. The FBI report, released on Wednesday, found that the so-called active-shooter incidents have more than doubled over the past seven years.

The agency identified 160 active shootings from 2000 to 2013 in which an individual killed or attempted to kill people in a confined or populated area.

The 2012 shooting at a movie theater in Aurora and the Sandy Hook Elementary School incident in Newtown are two notable shootings during this period.

On December 14, 2012, twenty children and six adult victims were fatally shot by a gunman -- who later killed himself -- at the Sandy Hook Elementary School in the town of Newtown in the U.S. state of Connecticut. Earlier that day, the assailant also killed his mother in another location.

There have been reports that the twenty-year-old killer, Adam Lanza, suffered from a personality disorder, was on the antidepressant Prozac, and was fond of first-person shooter games.

Every year, more than 30,000 people are shot and killed in the United States. The U.S. averages 87 gun deaths each day as a function of gun violence, with an average of 183 injured, according to the University of Chicago Crime Lab and the Centers for Disease Control.

The year 2012 was a record setting year for gun sales in the United States. About 4.5 million firearms are sold annually in the United States at a cost of 2 to 3 billion dollars.