HOUSTON, Texas

The suspected gunman in the deadly Highland Park Fourth of July parade shooting in the US state of Illinois pleaded “not guilty” Wednesday to the 117 charges against him.

Robert Crimo III, 21, entered the plea at his arraignment at the Lake County Courthouse in Waukegan.

Seven people were killed during the mass shooting on July 4. More than 40 others were injured.

The most serious charges he faces are 21 counts of first-degree murder, three counts for each victim killed during the attack, according to the Lake County State's Attorney's office.

Prosecutors said the suspect also faces 48 counts of attempted murder and 48 counts of aggravated battery with a firearm "for each victim who was struck by a bullet, bullet fragment, or shrapnel."

Authorities said the suspect confessed in detail to the shooting after he was arrested four hours after the deadly rampage.

"We do believe (he) pre-planned this attack for several weeks," said Sgt. Christopher Covelli of the Lake County Major Crimes Task Force at a news conference. "He brought a high-powered rifle to this parade, he accessed the roof of a business via a fire escape ladder and began opening fire on the innocent Independence Day celebration goers."

Police said the suspect legally purchased the high-powered rifle used in the attack and the weapons retrieved from the shooting scene and his vehicle were registered in his name.

The judge ruled that Crimo would be held without bond and that there was probable cause to hold him for seven counts of first-degree murder.

Crimo has not released a motive for the deadly shooting.

If convicted of first-degree murder, he faces a mandatory sentence of life in prison without parole.

His next court date is scheduled for Nov. 1.