According to a police statement, the pitcher shot and killed 25-year-old Michel Castillo Almonte and wounded his 17-year-old brother during a New Year's Eve celebration in the northeast coastal town of Luperon.
No motive was disclosed. Simon is from the Dominican Republic, and police said he fled after the violence.
Felipe Alou Jr., a Dominican representative for the Orioles, said he spoke with Simon on Saturday and the player insisted he was not involved in the New Year's Eve shootings.
The 29-year-old Simon joined Baltimore in 2008 but was quickly sidelined with an injury. He went 4-2 with a 4.93 ERA last season. He had 17 saves before Orioles manager Buck Showalter decided to make Koji Uehara the closer.
Simon could face up to 30 years in prison if found guilty.
The Associated Press contributed to this report.