The 13-year-old allegedly kept his hat on as the US national anthem played

A Montana man allegedly slammed a boy's head to the ground at a county fair because the 13-year-old kept his hat on during the national anthem, a witness told local news outlets.

In a news release, Mineral County Sheriff Mike Boone said witnesses identified the suspect as 39-year-old Curt James Brockway. Brockway was apprehended at the fairgrounds, located in the western Montana town of Superior, and charged with assault on a minor - a felony.

The sheriff's office declined to provide additional information on the alleged assault, including motive. But Taylor Henneck, who attended the event, told local news outlets she overheard the attack near the Mineral County fairground entrance, just as the national anthem began to play.

The woman said she heard a "pop," and turned to see the boy writhing on the ground.

"He was bleeding out of his ears, seizing on the ground, just not coherent," Henneck told The Missoulian. As startled spectators closed on Brockway, Hennick said he offered a simple defense for his actions.

"He said (the boy) was disrespecting the national anthem so he had every right to do that," she added.

Police say the child was rushed to a hospital Saturday then flown to Sacred Heart Children's Hospital in Spokane, Washington. KPAX, a CBS-affiliated news station, reports the boy suffered temporal skull fractures in the incident. His mother told the station her son's ears bled for six hours after the alleged assault.

By Tuesday, the boy had been released from the hospital and was recovering at home, she said.

"It's just a lot of pain in my head. I don't remember anything - the rodeo - the helicopter - nothing," the 13-year-old said in an interview with the station.

Controversy surrounding the national anthem dates back to 2016, when then-NFL star Colin Kaepernick called attention to police brutality and racial injustice by kneeling as the song played before games. The silent protests were largely condemned by many on the political right, including President Donald Trump - who in September 2017 encouraged teams' owners to fire players who knelt during the anthem.

It was not clear whether Brockway had an attorney, though he was scheduled to be released on his own recognizance Tuesday. The Missoulian reports that he was charged with assault with a weapon in 2010, resulting in a 10-year probation sentence.

Brockway's arraignment is set for Aug. 14.