After the Hampden County district attorney announced he was not going to charge police officers in a 2015 assault, the head of the Springfield NAACP and one of the victim’s lawyers expressed concern about too much — and too little — police involvement in the investigation.

The attack occurred outside a bar and left four men with injuries. As MassLive has reported, the men believed the assailants were off-duty Springfield police officers, but they weren’t able to identify them conclusively.

The president of the local NAACP, Bishop Talbert Swan, said it’s less than ideal that the DA had to rely on police department reports to try and build a case.

“I will encourage this district attorney, in cases like this, to call for an independent source from outside of Springfield,” Swan said. “Police investigating police winds up with this type of result.”

Michelle Cruz, the lawyer for one of the victims, said a lack of cooperation by police was also a problem.

“You have a number of officers taking the Fifth Amendment,” she said. “Those officers know who assaulted my client. They know. The police officers who responded know the identities of the individuals.”

Gulluni has expressed frustration with the case and told MassLive he hopes justice will be served through the police department’s disciplinary process or through a lawsuit.