Police have arrested a 20-year-old man who they believe shot his 22-year-old girlfriend, who died, on Friday afternoon.

Rodney Patterson was arrested after police believe he shot his girlfriend inside an apartment complex near 19th and Glendale avenues. They said the couple had "a troubled relationship."

According to the Phoenix Police Department, around 2 p.m. on Friday while officers were investigating an unrelated shots fired at a car call, neighbors living at an apartment complex near 19th and Glendale avenues told police they heard shots fired inside an apartment unit and also saw a man running away from the residence.

Police located the apartment where the shooting happened and found a woman, who was dead, inside the home. They said the woman appeared to have been shot.

Patterson was arrested by officers about a block and a half away from the apartment complex.

The woman's identity is not being released at this time.

Patterson was booked into jail and faces charges of 2nd degree murder.

Police said another man who was inside the residence at the time of the shooting has not been located and is still outstanding. A description of the man is unavailable at this time.