The Killer Priest

The Catholic Church is known for sweeping everything under the rug and keeping their secrets from coming out. In the 1990s, the public finally found out about the sexual abuse that was predominant in this religious institution. Having in mind that they managed to cover up numerous cases throughout the decades, it shouldn't come as a surprise that they also concealed a murder which shocked a small town of McAllen in 1960. 
Religious people from this area refused to believe that a priest was capable of such a thing, and the police had almost no evidence. The case went cold, and it collected dust for decades, waiting for someone to start talking. And luckily, one person decided to tell the investigators everything.