Story highlights

Video of the police response to reports of fighting at a pool party was posted to YouTube

The police chief says his actions in the video are "indefensible"

CNN  — 

The family of a Texas teenage girl is suing the city of McKinney, its police department and a former police officer for the fallout after a call about a “disturbance” at a neighborhood pool party in 2015.

In a federal complaint filed last month, 16-year-old Dajerria Becton and her legal guardian allege that former police officer Eric Casebolt violated her constitutional rights by using excessive force. CNN cannot independently verify the amount of damages the family is seeking.

A video posted to YouTube, captured Casebolt, cursing at several black teenagers, unholstering his gun before grabbing Becton in June 2015. He repeatedly slammed her face on the ground, forcefully straddled her while thrusting his knees into her back and neck, the footage shows.

Video of the incident went viral and ignited allegations of racism – critics publicly denounced the white officer for his aggressive actions.

“Civil rights were violated,” Attorney Kim T. Cole, representing Becton said at a press conference on Wednesday.

“When you’re in trouble, you should be able to rely on law enforcement to assist, not to have them attack you,” Cole said.

The lawsuit claims the city failed to properly train its police force, the senior officer on the scene, used excessive force and falsely arrested her.

“She was not a threat to the officer at any point throughout that event,” Cole said.

The teen was not accused of a crime, suspected or arrested for a crime, according to the lawsuit.

After the incident, Becton wasn’t charged, McKinney police said. She was released to her parents.

Though Becton’s physical injuries have healed, “the psychological damage from this attack will follow her for the rest of her existence,” her lawyer said.

Casebolt’s actions were described as “indefensible” by his former boss.

Casebolt was placed on administrative leave after the incident and resigned from his post as a corporal for the police department in McKinney shortly after.

A grand jury declined to indict Casebolt on any criminal charges, a law enforcement source in the Collin County told CNN.

Meanwhile, the city of McKinney has denied the allegations against it and the McKinney Police Department. The city plans to “vigorously defend the recently filed lawsuit,” a statement released on Wednesday said.

“McKinney prides itself in cultivating the highest standards of training and professionalism for our officers, and it strongly believes that its standards and training will withstand legal challenge.”

CNN’s Kayla Rodgers an Jason Morris contributed to this report.