Mass shootings have been occurring more frequently in recent years , an FBI study shows , with nearly one incident a month from 2000 to 2013 . The study , which was released Wednesday , reported 160 incidents during that time , with 486 people killed and 557 wounded . Those figures do n't include the deaths or injuries of the shooters . The bureau called such shootings `` active shooter incidents '' -- which the report described as `` individuals actively engaged in killing or attempting to kill people in populated areas ( excluding shootings related to gang or drug violence ) . '' Underscoring the difficulty authorities have to prevent such incidents or reduce their lethality , the study found that 60 % of the shootings ended before law enforcement officials arrived . In cases where investigators could determine the length of time of the incident , most of the shootings lasted under five minutes and many under two minutes . In 40 % of the cases studied , the shooters killed themselves . Most of the shootings were carried out by males . Only six of the `` active shooters '' in incidents during that time period were female . Seventy percent of the incidents `` occurred in either a commerce/business or educational environment , '' the FBI said . James Yacone , the FBI 's assistant director overseeing the Critical Incident Response Group , said at a briefing that the study is part of a White House-directed response to some of the recent mass shooting incidents and the need to understand what 's behind them and how to prevent them . Because police and other first-responders often also are shot or wounded , the FBI hopes to implement better practices for local agencies usually first on the scene . `` In essence , we 're trying to improve our readiness , '' Yacone said . Frequency increasing . And if you think such shootings seem to be happening more frequently in the past few years , you 're right . `` In the first half of the years studied , the average annual number of incidents was 6.4 , but that average rose in the second half of the study to 16.4 , an average of more than one incident per month , '' the study said . `` Recognizing the increased active shooter threat and the swiftness with which active shooter incidents unfold , these study results support the importance of training and exercises -- not only for law enforcement but also for citizens . '' The FBI said the goal of the study is to `` provide federal , state , and local law enforcement with accurate data so they can better understand how to prevent , prepare for , respond to , and recover from these incidents . '' Active shooter incidents differ from `` a defined crime , such as a murder or mass killing , '' the study says , because `` the active aspect inherently implies that both law enforcement personnel and citizens have the potential to affect the outcome of the event based upon their responses . '' 25 deadliest mass shootings in U.S. history . Andre Simons leads the FBI 's Behavioral Analysis Unit 2 in Quantico , Virginia , which is helping to study the motives for shootings and assists local police in detecting early signs that may indicate a suspect is planning one . Simons said at Wednesday 's briefing that while the motives vary widely , more shooters appear to be inspired by past mass shootings . `` The copycat phenomenon is real , '' Simons said . Anecdotal evidence shows that `` many active shooters have a real or perceived deeply held personal grievance and the only remedy that they can perceive for that grievance is an act of catastrophic violence against a person or an institution , '' Simons said . Many shooters research major shooting events and find inspiration from the notoriety that killers receive . `` As more and more notable and tragic events occur , we think we 're seeing more compromised and marginal individuals who are seeking inspiration from these past attacks , '' Simons said . Case studies . Among the incidents studied by the FBI for the report was the Sandy Hook Elementary School shooting in Newtown , Connecticut , on December 14 , 2012 . Gunman Adam Lanza , 20 , killed 20 children , ages 6 and 7 , and six adults at the school before killing himself . Police later found the body of Lanza 's mother at her home . `` 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 said . Another case studied for the report was the mass shooting at an Aurora , Colorado , movie theater in 2012 . Twelve people were killed and 58 wounded . Accused gunman James Holmes pleaded not guilty by reason of insanity to the killings ; his trial begins next month . In 2007 , Virginia Tech student Seung-Hui Cho shot and killed 32 people and wounded dozens more in a classroom building and a dorm on campus before killing himself . Maj. Nidal Malik Hasan killed 13 people and wounded 32 at Fort Hood , Texas , during a shooting rampage November 5 , 2009 . He was convicted and sentenced to death .
the past few years , there were only six `` active shooter '' incidents , Gunman Adam Lanza study shows . Most shootings were carried out by males -- 160 were female . 40 % of the incidents took place at schools or businesses , report says .