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

Prominent Active Shooter Events in the US

Nation	Date	Location	Killed	Injured
Unites States	August 4, 2019	Dayton, OH	10	27
United States	August 3, 2019	El Paso, TX	22	24
United States	May 31, 2019	Virginia Beach	13	4
United States	May 18, 2018	Santa Fe, TX	10	13
United States	Feb 14, 2018	Parkland, FL	17	14
United States	Sep 16, 2013	Washington Navy Yard shooting	12	3
United States	Dec 14, 2012	Newtown, CT – Sandy Hook	28	2
United States	Jul 20, 2012	Aurora, CO – Theatre Shooting	12	70
United States	Apr 16, 2007	Virginia Tech – Blacksburg, VA	33	17
United States	Apr 20, 1999	Littleton, Colorado – Columbine	15	21

 

Prominent Terrorist Attacks with coverage in the US Press

Nation	Date	Location	Killed	Injured
Russia	Apr 3, 2017	St. Petersburg Metro	10+	43+
United States	Jun 12, 2016	Orlando Night Club	49	53
Belgium	Mar 22, 2016	Brussels airport and metro bombings	35	300
United States	Dec 2, 2015	San Bernardino	14	22
France	Nov 13, 2015	Paris Attacks – Bataclan theatre	137	368
France	Jan 2015	Charlie Hebdo – Paris	17	22
Russia	Jan 24, 2011	Domodedovo Apt, Moscow, Russia	37	173
Russia	Mar 29, 2010	Moscow Metro bombings	40	102
United States	Nov 5, 2009	Fort Hood shooting	13	33
India	Nov 26, 2008	Mumbai gun and bomb attacks	166+	308+
United Kingdom	Jul 7, 2005	Underground bombings in London.	53	700+
Russia	Feb 6, 2004	Moscow Metro bombing.	41	102+
Russia	Oct 23, 2002	Moscow theater attack	170	700+

Worldwide Attacks by Islamist Terrorists since 1980:

Killed –> 17,271 | Injured –> 41,478

Source: Wikipedia