Two suspects have been arrested over the shooting death of a six-year-old boy, Aiden Leos, on a Southern California freeway,” CNN reports. The incident was allegedly triggered by a bout of road rage, according to the California Highway Patrol.

In a news release, the CHP said that 24-year-old Marcus Anthony Eriz and 23-year-old Wynne Lee were arrested at their Costa Mesa, California home on Sunday. It’s not clear how the two were tracked down, but their arrests came after a reward for info on them was bumped up from $450,000 to $500,000. Investigators said they received an “indescribable outpouring of concern and hundreds of tips.”

The two are being held on $1 million bond, and have a scheduled court appearance for Monday. They’re expected to be charged with murder. 

Investigators had been attempting to locate a white Volkswagen after the shooting, which occurred on May 21. Leos was being driven to his kindergarten class by his mother, Joanna Cloonan. Authorities say someone in another vehicle began shooting at their car. Leos was sitting in a booster seat when he was hit, and he told his mother his “tummy” hurt. He later died at the hospital.

Police say “some type of road-rage incident” involving Cloonan and another motorist preceded the shooting. The grievance had to do with a “perceived unsafe lane change,” according to CNN.

“Six-year-old Aiden should have been in kindergarten today, but instead his family is getting ready for his funeral tomorrow,” said Orange County District Attorney Todd Spitzer last week.

You can read the CHP’s entire press release below: