Police in Arvada, Colorado on Friday released details of the nature of the chemical device hurled at a police officer last week.

According to Fox News, an officer was responding to a suspicious package call when a young man threw a bottle at him. The bottle began to emit smoke containing chlorine, which caused the officer to pass out.

Backup officers arrived and summoned an ambulance to the scene. The officer and a bystander were transported to a nearby hospital. There, he was decontaminated and treated for his chemical exposure. He was diagnosed with sustaining a chlorine gas exposure.

Investigators used a found Walmart receipt to track down the subjects reportedly involved in the attack.

Five young adults—identified as Maxwell McCann, Braiden Ulmer, Isaac Koch, Gavin Dawson—and an unidentified juvenile are all suspects in the case. They were charged with possession of a chemical, biological or radiological weapon, among other charges.

The officer is expected to be okay.