While authorities in Illinois announced on Monday they would not pursue criminal charges in the case of a dead 21-year-old woman, her father vowed to continue looking for answers while suggesting her ex-boyfriend -- a civilian police dispatcher -- was being shielded from investigation.

"There is no doubt in my mind somebody murdered my daughter," Larry Young told KMOV-TV. "There's one person, the main suspect, he refuses to be interviewed by state police since it began."

Young's daughter, Molly Young, was found dead at the apartment of Richie Minton in March 2012, yet according to him, the state attorney's office has made little progress in the case, even though his daughter's body was found with a gunshot wound to the head despite Minton telling an emergency dispatcher that Molly Young "bled out through her nose" because of a drug overdose.

"I always say missteps and cover-ups are twins," Larry Young told KMOV. "They look alike but perform different functions. Cover-up is a big word, yes, and I'm not saying it until I prove what I see."

WSIL-TV reported that Jackson County State's Attorney Michael Carr said on Monday that there was not enough evidence to support a criminal investigation. A jury of six people came to a similar conclusion in January 2013.

"I'm going to get all the facts so that I can prove what's going here," Larry Young told WSIL. "You can assume a lot of things; there's suspicious actions going on by several different factions in this."

Larry Young also argued that he found no fingerprints on the gun allegedly responsible for the wound to his daughter's hand and that Minton moved her body before police arrived. Young has since established a social media campaign to bring more attention to the case.

"That 911 tape tells it all," Larry Young said to WSIL. "The guy's so calm on the 911 tape you'd think he was ordering a pizza or something."

Watch KMOV's story on the case of Molly Young's death, aired Monday, below.