San Francisco’s Fourth of July celebration along the city’s waterfront quickly turned into hours of gridlock, dangerous fireworks incidents and a surge in emergency calls.

Thousands packed Crissy Field to watch fireworks launched from the Golden Gate Bridge. But once the show ended, it wasn’t exactly a smooth ride home.

While many left with great memories. Others found themselves stuck for hours in gridlock, caught in a massive backup involving dozens of Waymo cars, while firefighters across the city were responding to fires and serious fireworks injuries.

For Rose Peterson, the ride home after San Francisco’s Fourth of July fireworks took an unexpected turn.

“We were pulling up to a four-way stop and this guy was shooting off a firework in the middle of the road, and then our Waymo starts driving, and we’re like ‘Wait, what’s happening?’,” she said.

No one inside was hurt, but Peterson says the experience left her questioning how autonomous vehicles respond in unpredictable situations.

“I definitely think it needs to be more sensitive of anything that can come into the path of the road,” she said.

That wasn’t the only challenge after the show.

As thousands left Crissy Field and the Presidio, traffic came to a standstill. Among those stuck was Dave Guingona, who had friends visiting from the Philippines and wanted to show them a memorable Fourth of July in San Francisco.

“Five minutes, 10 minutes, 15 minutes went by, then we realized people were getting out of their cars, yelling and screaming at these Waymos because there were no drivers,” he said.

He says nearly two hours later, Waymo employees finally began driving the vehicles out.

“They had a great time, but this is what they’re going to remember for the rest of their lives. This was unbelievable,” he said.

While traffic barely moved, San Francisco firefighters responded to more than 500 calls for service, including four fireworks-related wildfires, numerous outside fires across the city and a vehicle fire on Connecticut Street believed to have been sparked by illegal fireworks.

Crews also responded to two life-altering fireworks injuries.

Captain Jonathan Baxter says the incident Peterson experienced in the Waymo was another reminder of how quickly things could have turned tragic.

 “That situation could’ve had a far worse outcome—not only for the individuals in the car that could’ve been injured or worse—but for the individuals who lit the fireworks. They could have their life altered for the rest of their lives as well,” Baxter said.

Waymo says extreme traffic congestion disrupted operations for several vehicles after the fireworks and crews worked with city officials to clear them from the area.

The company also says it’s evaluating the incident surrounding fireworks, adding it’s committed to learning from situations like this.

San Francisco fire officials are reminding people that even fireworks marketed as “safe” can cause devastating injuries and fires. As for Waymo, the company says it’s reviewing both last night’s traffic congestion and the incident involving Rose’s ride as it looks for ways to improve operations during major events.