A man riding a Divvy bike was critically injured after being struck by two vehicles on Lake Shore Drive early Saturday, police said. View Full Caption DNAinfo file photo

CHICAGO — A man riding a Divvy bike was critically injured after being struck by two vehicles, including an Uber cab, on Lake Shore Drive early Saturday, police and a witness said.

The incident happened around 2:50 a.m. in the 3100 block of North Lake Shore Drive, south of the Belmont Aveune exit in Lakeview, according to Officer Ana Pacheco, a Chicago police spokeswoman.

The 24-year-old cyclist was riding northbound on outer Lake Shore Drive when he began swerving between the two right lanes, police said, citing a witness account of the driver of a 2008 Mitsubishi sedan.

The cyclist then collided with the Mitsubishi and was thrown under the car, police said.

Another motorist, driving a 2011 Nissan, stopped to help the cyclist. But the driver of a 2001 Honda Civic was unable to stop in time; the car swerved, hitting the Nissan, the cyclist and then the Mitsubishi, police said.

The cyclist was transported to Advocate Illinois Masonic Hospital where he is in "very critical" condition, Pacheco said. Police said alcohol is thought to have played a "major factor" in the crash.

The 22-year-old driver of the Honda was cited for driving an uninsured vehicle, police said.

The first car that collided with the cyclist was an Uber cab, said Jefferson Park resident Edgar Oprondek, 33, who was the car's passenger. He said events unfolded quickly.

"My Uber driver hit the brakes, and went left. The (cyclist) also went left, went further than our car," he said. The cyclist hit the car's mirror, knocking it off, and fell to the ground, Oprondek said.

The man tried to get up as Oprondek and his driver called authorities, and attempted to warn other drivers. But another car swerved into the accident, striking the cyclist again and pushing him under the Uber cab, as Oprondek and the driver dove over a concerete barrier to safety, he said.

"We just couldn’t even do anything for the guy on the ground," he said. Oprondek said the cyclist's left foot was severed, and he had a large cut on his head.

"I feel so bad for him and everyone else involved; it’s a terrible situation," he said. "There’s never a good time for it, especially ... with family get togethers and what not" on the horizon.

"It's unsettling," Orpondek said.

No other information was immediately available.

The Major Accidents Investigation Unit is investigating.

For more neighborhood news, listen to DNAinfo Radio here: