A West Mifflin man has been charged with killing his roommate.

Police say 20-year-old Andy-Steven Nimajuan-Sitan and his roommate, identified as Mario Alejandro Perez Santos, were drinking in their trailer along the 1100 block of Thompson Run Road when, at some point, the two started fighting.

Inside the home, first responders found Perez Santos deceased with significant trauma to his head and multiple puncture wounds, while Nimajuan-Sitan was injured.

Nimajuan-Sitan was taken to the hospital to be treated for lacerations, police said. His condition was last reported as stable. 

According to the criminal complaint, the fight escalated to the point where a knife and a baseball bat were used during the incident. Nimajuan-Sitan told police that Perez Santos initiated the fight and came after him with the knife.

Allegheny County police and the District Attorney's Office are investigating the incident. They are charging Nimajuan-Sitan with criminal homicide. He is being held in the Allegheny County Jail.

Anyone with information on the incident is asked to call the Allegheny County Tip Line at 1-833-ALL-TIPS. Callers can remain anonymous.