The number of mass shootings in the US has dramatically increased in recent years, with nearly a quarter taking place in schools or universities.
An FBI report which looked at the number of "active shooting incidents" in the US found that 480 people were killed and 557 injured between 2000 and 2013 because of a person or people firing in a populated area.
The report found that between 2000 and 2007, there was an average of 6.4 shootings in the US a year. In the next seven years, this figure rose to an average of 16.4 incidents annually.
The average number of deaths in shootings were also higher in the last seven years, with 2012 shown to be the most violent year in the study, when 90 people died and a further 118 were injured.
This includes the 2012 cinema shooting in Aurora, Colorado, in which 12 people were killed and a further 58 wounded, and the Sandy Hook Elementary school massacre in which 26 people - including 20 children - were shot.
The reports also states that all but two of the shootings involved a lone gunman, and only six of the total number of shooters were women.
Of the 160 mass shootings over the past 14 year period, 45.6% of them occurred in areas of commerce such as shopping centres or business areas open to pedestrians.
Educational environments were identified as the second-largest location for mass shooting to occur with 24.4% of the total. These were further broken down as those occurring in schools (16.9%) and Institutions of Higher Education (7.5%).
The FBI said the goal of the study was to provide federal, state, and local law enforcement authorities with accurate data so they can "better understand how to prevent, prepare for, respond to, and recover from these incidents."
The report states 60% of all the shootings were over before police arrived on the scene. In 21 of the 45 incidents where police were involved in stopping the shooter, nine officers were killed and 28 were wounded.
A total of 90 incidents ended on the shooter's initiative, such as suicide or fleeing. A further 21 incidents ended after unarmed citizens successfully restrained the shooter, including 11 by school employees or students.
"In at least nine incidents, the shooter first shot and killed a family member(s) in a residence before moving to a more public location to continue shooting," the FBI report added.
James Yacone, an FBI assistant director who helped with the report, said: "These incidents, the large majority of them, are over in minutes. So it's going to have to be a teaching and training of the best tactics, techniques and procedures to our state and local partners.
Special Agent Katherine Schweit, who heads the FBI's Active Shooter Initiative, says as a majority of the shootings are over so soon, she hopes the study "demonstrates the need not only for enhanced preparation on the part of law enforcement and other first responders, but also for civilians to be engaged in discussions and training on decisions they'd have to make in an active shooter situation."