Dahlquist, 19, died of carbon monoxide poisoning and smoke inhalation on Aug. 12 after his roommates and a friend lit roman candles under his bedroom door as a prank after a night of drinking.
"There were some Roman candles that were being ignited under the door,"Peoria County Lieutenant Mark Greskoviak said. "Dahlquist's bedroom was apparently closed when he went to bed that night. They were shot under the door into his room."
Dahlquist's roommates and teammates Ryan Johnson, Nick Mentgen, David Crady and friend Daniel Cox have been charged with aggravated arson and possession of explosives.
They tried to save Dahlquist but were driven away by intense heat, according to authorities.
Dahlquist's blood-alcohol content at the time of his death was .155%.
All four students are due back in Peoria County Circuit Nov. 2 for a review hearing.