Officer Perez said Rosario was dead when the police arrived at the house.
Officer Perez said that the suspect told her at least 10 people had beaten him up.
"He's just a small, little young kid," said Officer Perez.
Jose's mother had told him that if he was mugged, to offer no resistance and "give it up," said Officer Perez.
Officer Perez, 28, was the third officer killed in the line of duty this year.
Like many police officers, Officer Perez linked his anger to his economic anxiety.
"He sits at a desk over in City Hall taking full credit for what the police officers have done," said Officer Perez.
The two men also interviewed the prosecutor in Officer Perez's case.
But police officials said it was appropriate to continue administrative proceedings against Officer Perez.
Officer Perez, a member of the police force for eight years, was assigned to the department's crime-prevention division.