(CNN)A driver plowed into a sidewalk several times at the Las Vegas Strip, injuring more than 30 pedestrians in what authorities described as an "intentional" act.

At least one person was killed and 37 others injured near the Paris Las Vegas hotel Sunday night, authorities said.

The driver is in custody, and undergoing tests for alcohol and controlled substances. A 3-year-old in the car with her was unharmed.

Authorities ruled out terrorism and disputed witnesses' reports of gunshots.

"This was not an act of terrorism," Deputy Police Chief Brett Zimmerman said. "We are treating this as an intentional act."

The driver, who is in her 20s, went on the sidewalk three or four times, according to Zimmerman.

He said the homicide division is investigating, and is looking at numerous surveillance videos from the Strip.Antonio Nassar, who was at the Strip, said people scrambled to stop the driver as she careened into the sidewalk.

"The car rolled right in front of me. By the time I looked over to the right, all you could see was [her] driving away and people were bouncing off the front of the car," Nassar told CNN affiliate KLAS.

"She rode the sidewalk, she came to a stop at the Paris intersection, people are punching into the window ... she accelerated again and just kept mowing people down."

Rows of ambulances and police cars gathered at the scene, their lights flickering.Witnesses described disturbing scenes as crowds fled.

"Everyone was running ... and as I was running, I saw a car up on the sidewalk coming toward us," a witness told the affiliate. "I saw a lady, she didn't seem like she wanted to stop the car, she had both hands on her wheel and she was looking straight forward."

Others tried to stop the driver and drag the toddler out, she said.

"I saw men running after her, yelling, 'stop, stop!' As she was passing, we saw people running after her. Everyone was so frantic and just running around."

Traffic snaked down the streets as cars were diverted near the Paris Las Vegas hotel.

As the night wore on, the streets emptied.