SWAT teams are comprised of police officers trained to use “special weapons and tactics,” and they have been front and center in photos and footage of protests in Ferguson, Mo.

According to Jack Greene, who teaches criminology at Northeastern University, these tactical teams were created in the 1960s with a simple objective: “They are there to deal with high violence, high profile situations.”

It used to be only big departments in big cities had SWAT teams, says David Harris, a policing expert at the University of Pittsburgh School of Law. “Now, most departments of any size, except for the very smallest ones, have a SWAT team.”

These departments are worried about terrorism and other threats.

But, Harris says, there are departments that just want to keep up with other departments: “You have situations where we wouldn’t have thought in the past you needed a SWAT team, and the SWAT team is there, shows up, and it’s ready to go.”

Many departments, Harris argues, could spend more time thinking about equipment and training, “using it in a way and only in situations where it makes sense,” and recognizing that the weapons, the uniforms, and the armored vehicles all send a very powerful message.