COSTA MESA — Off-duty Newport Beach Battalion Chief Todd Knipp was waiting for his son in an orthodontist's office when someone burst in and said a tree fell on a car across the corner.

Knipp told those around him to call 911 and raced downstairs to the scene at 17th Street and Irvine Avenue.

"First thing I did was check to see if there was immediately a problem with the driver and then check to see how many victims or patients we'd have in the car," Knipp said. "My first thought was given the time of day and location that I was just praying there wasn't any kids in the car."

There were no children inside the blue 2002 Hyundai. But 29-year-old Haeyoon Miller, a childhood musical prodigy who lived in Tustin with her boyfriend, was trapped in the coupe beneath the 50-foot blue gum eucalyptus that officials later said weighed 10 tons.

"I tried to communicate with her, but she was absolutely unresponsive," Knipp said. "There was very labored breathing, but no other signs of movement."

Multiple witnesses reported Miller being awake and talking with bystanders after the crash. Knipp and firefighters, who were on the scene within minutes, said that was untrue — Miller was unresponsive.

"I can tell you that there were people calling out to her and communicating in a hopeful tone," he said. "Someone may interpret that as [Miller] communicating with them. Maybe they didn't hear the other end of that communication."

Wearing a T-shirt, sandals and shorts, Knipp began to assess the situation — the best entrance for emergency vehicles, necessary equipment, and moving bystanders out of the way for the oncoming convoy of fire trucks, police cars and ambulances.

"Mostly people were kind of standing around with a shocked look on their face," Knipp said. "People were on their cell phones, people were yelling at her."

An off-duty paramedic was on the driver's side trying to communicate with Miller. Knipp said he was on the passenger's side. He said his view of Miller was obstructed by the collapsed roof. He could see Miller's arm but couldn't reach it.

"It's a very hopeless feeling," he said. "This is just one of those situations where you're going to have to get the heavy equipment to have any kind of impact on her outcome."

The first units to arrive immediately began sawing the 3-foot-wide trunk into sections, leaving a 9,000-pound portion atop Miller's roof. Crews used braces on either side of that piece and air bags to begin lifting it when it readjusted, resettling on the car.

Witnesses said it "fell" back onto the car, not a significant amount, but enough for them to notice. Firefighters said that depression was 4 to 6 inches and away from Miller's body.

Knipp said he's concerned the disparity in witness accounts from what he and other firefighters saw could be troubling for Miller's family.

"Unfortunately, I'm not a doctor, and I can't comment on the results of the autopsy," Knipp said.

A coroner's autopsy found Miller, who worked as an executive assistant at a mortgage office in Newport Beach, died as a result of blunt force trauma.

"I don't think there was a moment where she felt any of that," he said. "She was unresponsive. To have the family think she was trapped and suffering is a shame for the family. From the firefighters' point of view, we did everything that was humanly possible to get her out of there quickly."

Miller was pronounced dead at the scene.

The tree was maintained by the city of Newport Beach, though it was located inside Costa Mesa's city limits. Newport Beach city officials have not yet determined what felled the tree.

joseph.serna@latimes.com

Twitter: @JosephSerna