A 4-year-old boy shot in the head in Cleveland. A motorist who pointed a gun at a woman passing him on a Texas freeway. Another who police say fired his gun in the air five times after a woman honked her horn at him.

Experts say road rage incidents are on the rise across the U.S., with the above examples just the latest in a growing tally of dangerous behavior that often leads to violence.

In April, an analysis by The Trace, journalism startup that focuses on gun violence in the U.S., found that road rage incidents involving firearms more than doubled over three years, from 247 in 2014 to 620 in 2016, with at least 1,319 road rage episodes involving guns during that period. It said at least 354 people were wounded and 136 killed.

Law enforcement agencies don't collect information on road rage incidents as a specific category, so the organization's analysis was based only on incidents serious enough to warrant a call to police or a news outlet to publish a story.

The National Highway Traffic Safety Administration, however, does note a rise in traffic deaths involving aggressive driving — from 292 fatalities in 2011 to 467 in 2015, the last full year for data.

Experts blame the rise on a better economy putting more cars on the road — and therefore, more drivers in conflict.

Last year, the AAA Foundation for Traffic Safety released a study that said 8 in 10 U.S. drivers said they demonstrated anger, aggression or other forms of road rage at least once during the previous year. Nearly 8 million U.S. drivers went to extremes such as purposely ramming another vehicle or getting out of the car to confront another driver, it said.

"As the economy improves, we see that we have more drivers out on the road," AAA spokeswoman Tamra Johnson told NBC News. "Obviously more traffic can be a little more stressful for drivers."

The 4-year-old boy in Cleveland was last reported in serious condition following surgery to remove bullet fragments but was expected to recover. He was shot while his mother was driving him and his 7-year-old sister. She had honked her horn at a car blocking the road.

No arrests have been made.

And police in Lancaster, Texas, in the Dallas area, say charges are pending against a man who turned himself in after police received several tips that he was the driver who pointed a gun at motorist Victoria Best in the photo above, taken from a video she posted to Facebook that went viral. The man reportedly told police he was acting in self-defense and thought her cellphone was a weapon.

Best told WFAA-TV on Sunday that she was on her way to work Friday when the car in front of her started brake-checking her. "It was like he was trying to cause a rear-end accident," Best said. "That was what made me pick up my phone and start recording."

The summer season of rage kicked off with this incident in June, in which a car and motorcyclist mixed it up in Los Angeles. In the course of the altercation, the motorcyclist kicked the car, then the car lost control, triggering a chain-reaction crash.

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