How is this for something that's out of bounds? Police racing in their cars up to 120 miles per hour. And some were just going to the doughnut shop. Putting us all at risk in the process. Once again... See More
How is this for something that's out of bounds? Police racing in their cars up to 120 miles per hour. And some were just going to the doughnut shop. Putting us all at risk in the process. Once again matt gutman with the 20/20 speed trap. well over 80 right now. So there I was, humming down the highway in a dodge challenger, trying to chase down a speeding north carolina state trooper. Wow, you guys, this guy's going 70 in a 45 right now. Howdy get here? All started when we saw this video. It's a florida state trooper in hot pursuit of a motorist flying up i-95 at speeds up to 120 miles per hour. But this is no ordinary speed demon. It's a miami dade police officer. It is a miami police -- Reporter: The cop ignores the trooper's lights and sirens, and tears across lanes of traffic. Finally, seven minutes later he pulls over. Believing that only a criminal in a stolen car could drive so recklessly, the trooper approaches with gun drawn. Put up your hands out the window right now! Put your hands out the window! Reporter: What's the big need for speed? Turns out the cop was running late for his off duty job as a security guard. I had to get there by 7:00 and I didn't think I was going to make it. Reporter: And we discovered, this guy isn't some kind of lone wolf. All around the country others have learned speeding cops can kill. To be clear not talking about police responding to an emergency with lights and sirens on. When cops gun it, the results can be lethal. Look at this. It's 2:15 a.M. On this connecticut road. A milford police department car speeding in a 40 mile per hour zone. Suddenly, another cruiser rockets past at 94 miles per hour and rams into a passenger car. Killed in the accident were two 19-year old sweethearts -- ashlie krakowski, a high school hockey star with dreams of becoming a nurse and david servin, a talented musician who planned to go to business school. When we found out what exactly happened, it was unbelievable. Did it make it hurt worse when you learned it was a police officer that hit them? You see them racing around all the time. And you know, this time they didn't get away with it. Reporter: So why do cops speed? Because they can. Reporter: Justin hopson is a former new jersey state trooper who wrote a book on corruption in his agency called "breaking the blue wall." And when they're speeding, where are they going? Home? Lunch. It's the mentality of hey, i have a badge, and the ability to go as fast as I need to go. Reporter: It's gotten so out of handsome motorists strike back. Catching speeding cops in the act. Watch this. A caravan of hot rods races down a new jersey highway at speeds over 100 miles an hour. A new jersey state trooper suddenly appears. He's going to put a stop to this, right? Wrong. He shoots ahead of them to lead the way. He's going to give them an escort by state police! Reporter: That pied-piper of sports cars was spended. This angry motorcyist with a helmet cam turns vigilante and takes off after a fast-moving police cruiser just to prove how fast he's going. Folks, don't try this at home. I'm going 20 miles an hour over the speed limit right now. Reporter: But none of the highway video avengers can match ron carr of raleigh, north carolina. After getting his hair blown back by lead-footed lawmen once too often, carr rigged his vehicle with cameras to expose what he calls rampant hypocrisy. Watch this guy. You or I would get a ticket for doing what he's doing right now. Reporter: Yes, they're fast and he's furious. Who's policing the police? What does it take for an officer to be charged? Reporter: Carr's now posting his greatest hits on, what else, his own youtube channel. I figured the more videos that I have, then folks will realize that it is a common problem. Reporter: But it's a problem that police departments seem reluctant to acknowledge. Going back to that terrible connecticut crash, the officer involved was convicted and sentenced to 10 years in prison. Though he's currently free as he appeals. The families of those two young victims wanted to uncover the scale of the problem, so they sued the police, demanding to see all dash cam video from the previous two years. We wanted to know was there a culture of speeding? Was this an isolated incident that you could forgive a little more easily? Reporter: The families did receive 500 dash cam clips, including footage of an officer on a call racing at 113 miles per hour in a 45 zone. He was suspended. But then the milford pd claimed it accidentally deleted another 2,000 dash cam clips. 2,000 clips, an accident? The family wasn't buying it. There appeared to be quite a culture of speeding to the extent that milford finally destroyed the tapes. They will not monitor each other. Reporter: Former trooper hopson says it's almost unheard of for cops to call each other out over speeding. If you do so, you're deemed a stool pigeon, and there's ramifications for doing that. Get out of the vehicle! Reporter: Want proof? Then turn back to that video of florida trooper donna watts. Remember she'd pulled over a miami police officer who was later fired from his department and is now trying to get his job back. Reporter: But watts says she was the one ultimately punished. After the incident she started receiving threatening phone calls and spotting strange police vehicles in front of her home. She's now suing, claiming the harassment made her life hell, prompting her to leave road patrol, even her home. Miss watts feels betrayed. For some members of the law enforcement community to turn against her has torn her apart. Reporter: We set up our own speed trap, chopper in the sky catching speeding cops led footed and red handed. We learned they weren't being pulled over for speeding. Do you think it's hypocritical police officers go 80 miles an hour and they would pull somebody like me over.
This transcript has been automatically generated and may not be 100% accurate.