Amid tear gas, rubber bullets and stun grenades, police are turning to a lesser-known crowd control agent: paintballs. Essentially no different than the ones a gaming enthusiast would use, paintball guns used by law enforcement compress air to fire small spheres that, upon impact, dispense liquid paint or an irritant powder. While companies that make paintballs guns tout them as safe tools for crowd dispersal, in reality, they carry significant risk. Even some police chiefs are now questioning their use.
For years, paintball guns have been used against protesters all over the world — in Benin, Turkey, Hong Kong and Mexico — but it is relatively new to see them used in the United States against protesters, said Brian Castner, an investigator at Amnesty International focusing on weapons.
The problem is that a paintball gun is associated with pretend war games and is often thought of as an innocuous toy. “The threshold for its use is low,” he said.
“You are seeing a lot more of this,” said Chris Burbank, vice president of law enforcement strategy of the Center for Policing Equity, a think tank, and the police chief of the Salt Lake City Police Department until 2015. “It seemed like a broader tactic than I had anticipated.”
In recreational paintball, players are required to wear ballistic eye protection, but people at protests tend not to wear protective gear. At least one study found paintballs pose significant risk for devastating ocular trauma.
Adam Keup said an officer, without warning, shot him in the eye with a paintball gun loaded with a ball of pepper spray at a protest in Omaha, Neb., in late May. Mr. Keup, 23, said doctors told him he would have permanent eye damage and might never be able to see out of that eye again.
“I was in a state of shock,” said Mr. Keup, who was hit while he was watching the protest from a distance and not participating. “It felt like getting a paper cut across your eye.”
Mr. Keup, a financial adviser, has experienced internal bleeding in his right eye and his lids are swollen shut. He is so sensitive to light that he has spent almost all of his time in dark rooms at home.
“As far as my day to day, I’m pretty emotional,” he said.
While the police typically say they try aim for the torso, back or buttocks to avoid eye injuries, paintballs can easily veer in other directions.
Teresa Nelson, legal director for the American Civil Liberties Union of Minnesota, said paintballs are “lethal in disguise.”
In recent years, police have stocked up on more than just paintball guns: They have added more firepower and military gear, especially in larger cities, where they use federal grant money to buy armored cars and other tactical gear.
Sometimes other types of projectiles used by the police are confused with paintballs. In a video posted on Twitter that has been viewed more than 28 million times, officers shot at a group of friends in Minneapolis who were on their front porch watching a National Guard Humvee drive down their residential street. “Light ‘em up!” said one officer, shortly after he yelled at the group to go inside. Within seconds, another officer started firing shots at them.
“What was terrifying is we didn’t know what they were firing,” said Tanya Kerssen, 38, a writer and researcher. The fluorescent marks on the torsos of her friends who had been hit were caused by a plastic projectile with paint marker.
One of the friends who was hit, Sam Rhode, said it felt like a sharp, stinging pain. In the two weeks since, the gash has grown into an eight-inch bruise.
“If they had one guy talk to people and say, ‘Here’s why you need to go inside,’ it wouldn’t have taken them any more time,” said Mr. Rhode, 44.
Thor Eells, executive director of the National Tactical Officers Association, which represents nearly 40,000 law enforcement professionals, said police have used paintballs for two decades, but they are more visible now because of the need.
“These are unfortunately necessary tools that have to be used now given the level of violence and destruction that has taken place,” said Mr. Eells, a former commander of the Colorado Springs Police Department.
Howard Jordan, the police chief of Oakland between 2011 and 2013 during the Occupy protests, said Oakland had mixed results with using paintballs. Ideally, they help identify people who police may later want to arrest because of the marks they leave.
But in reality, Mr. Jordan said, identifying protesters with paint rarely works. “People don’t usually stick around after they get shot with a paintball.”
Chief Art Acevedo of the Houston Police said his department of more than 5,000 law enforcement officers uses paintballs only for training. As president of the Major Cities Chiefs Association, a network of chiefs and sheriffs in the largest cities in the United States and Canada, he plans to discuss and evaluate the use of paintballs, among other tools police have used against violent protesters, in an upcoming meeting.
“We’re going to discuss the good, the bad and the ugly,” he said. “It’s important for everyone to take a step back and look at the circumstances in which we’re deploying these munitions and if there is a better way.”
Mr. Keup, the man who was shot in the eye, said that growing up, he always had respect and appreciation for law enforcement officials.
Now, he feels anxiety even when he passes police cars. “I don’t trust them,” he said. “I don’t feel like it’s safe to go in anywhere where there is a big police presence.”
John Ismay contributed reporting.