Terrifying video shows a group of teens brutally beating a man in broad daylight in the middle of a busy Los Angeles intersection.

The footage was posted Saturday on Instagram by a passenger in a Lyft car with a driver who is a former military officer.

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The pair jumped out of the vehicle to assist the victim — knowing full well they could become victims too — but the assailants got back onto their bikes and peddled off.

Before the suspects fled, an Uber driver shot video of them beating the hell out of the victim for unknown reasons.

The victim was seen laying like a rag doll in the street. Minutes later, police and paramedics responded to the scene.

Prior to their arrival, the Uber driver had to leave, but gave the assault video to the Lyft passenger to turn over to law enforcement. The passenger tagged the Los Angeles Police Department in his IG post.

The LAPD tells TMZ ... a group of teen cyclists got into an argument with a motorist and it escalated into a violent altercation.

Cops say the suspects then vandalized the victim's car before riding off -- and the bikers are still at large. The victim suffered a minor injury, which did not require hospitalization.