A cycling mob is the last thing one would expect to see in an area reserved for motor vehicles such as Boston’s O’Neill Tunnel.

However, that’s exactly what many drivers witnessed on Saturday evening when dozens of teens were spotted riding their bicycles through the tunnel. According to Massachusetts State Police, approximately 30 teenagers on bicycles entered the tunnel from Leverett Circle at around 6:30 p.m. on Saturday.

Many videos popped on social media showing the overly enthusiastic cyclists riding alongside cars, seemingly unaware of the danger they put themselves in. A tragedy could have happened as drivers who entered the tunnel suddenly had to slam on the brakes to avoid hitting the bicyclists. There’s a 45 mph (72 mph) speed limit inside the tunnel.

MORE: State Police say they were called – teens entered the tunnel at Leverett Circle. Troopers forced them out of the tunnel and they all took off, police didn’t pursue. pic.twitter.com/1Dc0BIpNO1

— Elysia Rodriguez (@ElysiaBoston25) April 1, 2019

Fortunately for the riders, someone else thought about their safety. When William Dyer saw his truck surrounded by the bikes, he believed the scene was actually for a movie. However, when he realized that wasn’t the case, he made sure the young cyclists were safe.

“That’s when I put my hazards on, and I stayed behind them so no one would get hit because we were going around corners and people were beeping the horn. I was afraid someone was going to get hurt, it was dangerous,” Dyer told Boston25News.

The police said it responded to 911 calls from the tunnel and forced the cyclists out at South Station. However, once the group was out of the tunnel it fled the scene and the troopers did not pursue. According to the Massachusetts Department of Transportation, the cycling mob was also spotted on the Zakim Bridge on Saturday.