Heavily equipped police responding to protests in Ferguson last week. Images and video of the events spreading on social media have brought this story to national and international prominence. - 

After President Barack Obama saw images and video from Ferguson, Mo., where a police officer shot an unarmed 18-year-old over the weekend, he urged police there to be “open and transparent.” He also called for officers and protesters alike “to take a step back and think.” 

Five days after the shooting, protests have swelled, and the police have been using what looks like pretty sophisticated, military-style weapons and gear. Many police departments across the country have that kind of equipment. And thanks to federal government programs, they have been amassing more of it.

The Pentagon has what it calls a “Disposition Services” department. Its mandate, quite simply, is to dispose of stuff.  A list of what’s available includes night-vision goggles, combat uniforms, tear gas, grenades and M16s.

Robert Kane heads the department of criminology and justice studies at Drexel University, and he says the Defense Department has sold billions of dollars of equipment at bargain basement prices.

“You know, an armored personnel carrier can cost somewhere along the lines of $780,000, maybe even $800,000, and sometimes the police department can get that for $3,000,” he says.

There are also grants available, Kane says.

State and local police departments have dealt with the DOD for decades, but Congress formalized that relationship in the 1990s, during the war on drugs and after the Los Angeles riots.

“Law enforcement was in many instances outgunned and out-equipped from a technical standpoint,” says Jim Pasco, executive director of the Fraternal Order of Police.

 After Sept. 11, departments acquired new surveillance equipment, along with new vehicles and weapons. 

David Harris, a law professor at the University of Pittsburgh, worries some departments rely on these high-end tools more and more. “You’ve got the stuff," he says. "'Isn’t this the occasion to use it?’ goes the thinking.”

You'd use it to break up protests. Even to deliver a warrant.

“When you militarize the equipment, and you militarize the personnel, you are also militarizing the situation and that can lead to escalation,” Harris says.

Police need the best training and the most suitable weapons, he says, but departments need to consider carefully how and when they use them.

Follow David Gura at @davidgura