Biden campaign cancels Texas event after Trump supporters surround bus on interstate

According to a source familiar with the incident, the vehicles were a "Trump Train group." These groups are known in parts of the state and organize events that involve their cars with flags and Trump paraphernalia and drive around to show support for the President. The group began yelling profanities and obscenities and then blockaded the entire Biden entourage.

At one point they slowed the tour bus to roughly 20 mph on Interstate 35, the campaign official said. The vehicles slowed down to try to stop the bus in the middle of the highway. The source said there were nearly 100 vehicles around the campaign bus. Biden staffers were rattled by the event, the source said, though no one was hurt.

Neither Biden nor his running mate, California Sen. Kamala Harris, were on the bus.

Staffers on the bus called 911, which eventually led to local law enforcement assisting the bus to its destination. The Biden campaign, out of what was described as an abundance of caution, ended up canceling an event scheduled for later that day in Austin, the aide said.

Texas State Rep. Rafael Anchía told CNN's Ed Lavandera that Wendy Davis was on the bus. Davis is a former state senator who is challenging Rep. Chip Roy for the Texas Hill Country area congressional seat.

"Rather than engage in productive conversation about the drastically different visions that Joe Biden and Donald Trump have for our country, Trump supporters in Texas today instead decided to put our staff, surrogates, supporters, and others in harm's way," Biden campaign Texas communications director Tariq Thowfeek told CNN.

"Our supporters will continue to organize their communities for Joe Biden, Kamala Harris and Democrats up and down the ballot, and to the Texans who disrupted our events today: We'll see you on November 3rd," Thowfeek said.

CNN has reached out to the Trump campaign for comment.