CNN  — 

A ferry ushering families from a popular sand sculpting competition in Florida was struck by a recreational boat Sunday evening in an apparent hit-and-run, killing one ferry passenger and injuring several others, police and witnesses said.

Brenda Alvarez, who is about eight months pregnant, was on the ferry with her husband and two young children when a crew member started yelling, “Hey, hey hey!” the family told CNN affiliate WFTS.

Alvarez’s husband turned around to see a large boat “just come through” the ferry, he said.

The other boat “shattered the whole back of” the ferry and “left a huge dent,” Brenda Alvarez told WFTS. “We can’t understand how fast they were going.”

The ferry was carrying people to and from the Sugar Sand Festival in Clearwater, WFTS reported. About 45 people were on board, including two crew members, police said.

Around 8:40 p.m. ET, authorities were notified that a boat had struck the ferry near the Clearwater Memorial Causeway Bridge, police said.

Officers arrived to find a “chaotic scene,” Clearwater police spokesperson Rob Shaw told CNN affiliate Bay News 9. Nearby “good Samaritans” used their own boats to help evacuate passengers.

The ferry came to rest on a sandbar, so some on board were able to walk to shore. But “firefighters had to go into the water and help some people,” Shaw said.

Six people were declared “trauma alerts,” including two who were “seriously injured” and airlifted from the scene by helicopter, Shaw said. One of the injured later died.

Early Monday morning, the US Coast Guard said one person had died and “12 people were transported to a local hospital.”

The incident was declared “a mass casualty incident by the fire department due to the number of injuries,” Clearwater police said.

Everyone who was injured in the crash was on the ferry, police said. “It is not believed that there is anyone reported missing from the ferry,” Shaw told CNN.

Kristin Vincelli, who was also leaving the festival, shared video with CNN showing emergency vehicles rushing toward the waterfront.

The recreational boat that struck the ferry fled the scene, but it has been identified by another law enforcement agency, Shaw said.

Six people were believed to be on the recreational boat, the US Coast Guard said, citing on-scene reports. Crews from the Coast Guard’s Station Sand Key were among the agencies that responded to the collision.

So far, authorities have released few details about the boat that hit the ferry.

“We believe our law enforcement partners are at another location with that boat,” Shaw told WFTS. He urged any witnesses to come forward with more information or video of the crash.

The Florida Fish and Wildlife Conservation Commission will be leading the investigation into the crash, Clearwater police said.

This story has been updated with additional information.