Kristie Cox lost nearly everything because of a missing safety pin and chain.

An improperly hitched trailer broke free on the road, slamming into her husband's SUV, tearing through its windshield and crushing the vehicle's left side. Her husband, Jeremy, and her 3-year-old daughter, Izzy, were both killed instantly. Only her son, Liam, survived.

"I just fell to the ground," Cox said. "How can they be gone? They're my life. They're every part of my life."

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According to federal officials, unhitched trailers have killed more than 300 people in recent years. In many cases, the trailers aren't latched properly, and can pop off — which is why most states require two safety chains as backups.

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"They become a weapon," said Lt. Brian Orr of the Oklahoma Highway Patrol. "They're a missile going down the highway."

It's such a big problem that Oklahoma's state police patrol for it every day. When TODAY tagged along with them, they quickly found trailers that could be dangerous, sharing the road with you.

One driver admitted he'd been out all day without chains, and promised to fix it. Within a minute, police spotted another trailer in violations and pulled the driver over.

"You only had one chain connected to your trailer," Orr told him. "You're required to have at least two."

The driver said the chain had broken and he didn't have time to get it fixed: A one-minute fix to a $10 part that could literally save lives.

"Two chains are pretty basic," Kristie Cox said. "That decision, which could have taken just moments, and [Jeremy and Izzy] would still be here today, and Liam would still have a daddy and a sister."

Police say unhitched trailer accidents are completely preventable. It only takes 30 to 60 seconds to secure trailers the right way.

Get step-by-step instructions on how to hitch up a trailer safely.

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