FITCHBURG — It was a horror movie come to life.

Judy Sanchez woke Thursday to the sound of heavy footsteps in her stairwell, followed by a loud motor. She got to her kitchen in time to see the blade of a chain saw rip through her front door.

“It was so crazy,” Judy Sanchez said. “I was terrified.”

Jan. 26 was the day of Operation Red Wolf, a multiagency sweep during which 16 people in Fitchburg were arrested on charges related to gang activity, drug trafficking and illegal gun sales after a two-year investigation by federal, state and local law-enforcement officers.

The people sawing through her door were FBI agents, looking for a gang member suspected of trafficking cocaine. But they went to the wrong address.

Sanchez said the ordeal traumatized her and her 3-year-old daughter, Ji’anni, and she is unsatisfied with the agency’s response to the error.

About 10 FBI agents came into her apartment at 391 Elm St., that morning, guns drawn and pointed at her. There was no knock, and they didn’t shout that they were from the FBI until after the saw was buzzing through her six-panel front door, she said.

She believes it took about three minutes for them to saw a big rectangle through the door, then kick in the center. She shouted repeatedly that they had the wrong place.

Once the first agent was inside, she was ordered facedown on the floor at gunpoint. Her 3-month-old pit-bull Lexi wet the floor, and she was instructed to grab the dog and hold her. To do so, she said, she had to reach through the dog’s urine.

Sanchez doesn’t know how long she was held on the floor, but estimates it was between 30 and 45 minutes while her daughter cried in the other room. It was a cold morning, and she was not allowed to put warm clothes on.

“I was still at gunpoint the whole time. I was freezing,” Sanchez said.

The FBI agents kept asking her where Luis Vasquez was, and she said she didn’t know.

Sanchez and her daughter live in apartment 2R, which is located in the rear of the building. The other apartment on the floor, 2F, is at the front and is the home of Luis R. “Joker” Vasquez, but Sanchez said she only knew him as “Jay.”

Vasquez, 41, is believed to be the leader of the local arm of the Sex, Money, Murda gang and was captured in his apartment. He faces up to 40 years in prison, a $5 million fine and lifetime supervision when released.

Tim Christmas, the former building manager, was called in to install a replacement door in Sanchez’ apartment. He estimated the fiberglass, prehung door unit he installed cost about $250.

The FBI will reimburse Lancaster Oaks Development, the company that owns the building, for the door.

Christmas also said he repaired the frame to Vasquez’s back door, which was pushed in for entrance.

“This is a big screw-up,” Christmas said.

He and Sanchez are both in disbelief that Vasquez could be involved in a gang, saying they thought he was a positive influence in the neighborhood and good with children.

A female FBI agent wrote down a number for Sanchez’s landlord to call for reimbursement for the door and the number for Damon Katz, chief counsel for the Boston division of the FBI. Sanchez said she received a quick oral apology that was devoid of remorse.

“Just a little pat on the back and saying ‘I’m sorry’ is not OK,” she said.

She said chain-sawing through a door may be common practice for the FBI, but it was a traumatic event for her and her daughter.

Sanchez attends classes at Fitchburg State University and didn’t go to class Thursday, feeling too disoriented. She’s having trouble sleeping now, and her daughter didn’t want to go into their bathroom all weekend because it is located next to the door the FBI used.

An FBI spokesman read a prepared statement about the incident.

“The mistake was quickly apparent to the FBI agents who entered the apartment. … The FBI assistant special agent in charge recognized legitimate concerns the resident had about the mistake,” the statement read.

The statement maintained that the agent that spoke with Sanchez apologized repeatedly and left her phone number and another number for any “further concerns.”

The FBI does not reveal specific operational details about the tactics of an arrest team, such as how long it takes to open a door. The spokesman said the agents typically wield M4 assault rifles and that it’s possible the shock of the event confused Sanchez about the length of time everything took.

The Fitchburg Police Department was not involved in the incident. Police spokesman Sgt. Glenn Fossa said he does not have direct knowledge of the details of the incident. He said the concept of compensation for property damage and trauma from a misdirected police raid is too broad a concept to identify a policy for what the department would do in a similar scenario.

Follow Michael Hartwell at Twitter.com/SEHartwell or Facebook.com/MichaelHartwell.