Barbecan Secure Entrance Systems would have prevented many prominent attacks, for example:

Prominent Active Shooter Events in the US

Unites StatesAugust 4, 2019Dayton, OH1027
United StatesAugust 3, 2019El Paso, TX2224
United StatesMay 31, 2019Virginia Beach134
United StatesMay 18, 2018Santa Fe, TX1013
United StatesFeb 14, 2018Parkland, FL1714
United StatesSep 16, 2013Washington Navy Yard shooting123
United StatesDec 14, 2012Newtown, CT – Sandy Hook282
United StatesJul 20, 2012Aurora, CO – Theatre Shooting1270
United StatesApr 16, 2007Virginia Tech – Blacksburg, VA3317
United StatesApr 20, 1999Littleton, Colorado - Columbine1521

Prominent Terrorist Attacks with coverage in the US Press

RussiaApr 3, 2017St. Petersburg Metro10+43+
United StatesJun 12, 2016Orlando Night Club4953
BelgiumMar 22, 2016Brussels airport and metro bombings35300
United StatesDec 2, 2015San Bernardino1422
FranceNov 13, 2015Paris Attacks - Bataclan theatre137368
FranceJan 2015Charlie Hebdo - Paris1722
RussiaJan 24, 2011Domodedovo Apt, Moscow, Russia37173
RussiaMar 29, 2010Moscow Metro bombings40102
United StatesNov 5, 2009Fort Hood shooting1333
IndiaNov 26, 2008Mumbai gun and bomb attacks166+308+
United KingdomJul 7, 2005Underground bombings in London.53700+
RussiaFeb 6, 2004Moscow Metro bombing.41102+
RussiaOct 23, 2002Moscow theater attack170700+

Worldwide Attacks by Islamist Terrorists since 1980:

Killed --> 17,271 | Injured --> 41,478

Source: Wikipedia