The Pittsburgh synagogue shooter was reportedly armed with an AR-15 — here's how it became the weapon of choice for America's mass shooters

Craftsman Veetek Witkowski holds a newly assembled AR-15 rifle at the Stag Arms company in New Britain, Conn, Wednesday, April 10, 2013. Associated Press/Charles Krupa

Parkland, Florida.

Las Vegas, Nevada.

Sutherland Springs, Texas.

Now, Pittsburgh, Pennsylvania.

Recent deadly mass shootings in these US cities have at least one thing in common: the AR-15.

The gunman who stormed The Tree of Life Synagogue and opened fire on Saturday, killing at least eight and wounded eight more in the suspected hate crime, was reportedly armed with the weapon.

The suspected gunman has been identified as 46-year-old Robert Bowers.

This weapon has become increasingly popular in the US, especially since the 1994 federal weapons ban expired in 2004, and has been used in many other mass shootings around the country. Not just the three listed above.

To understand how and why this has happened, we put together a historical overview of the weapon and spoke with David Chipman, a senior policy analyst at Giffords and former special agent with the Bureau of Alcohol, Tobacco, Firearms, and Explosives.

The National Rifle Association did not respond to our request for comment.