INVESTIGATORS in the killing of state university president Dr. Ricardo Rotoras are now looking into the material evidences to corroborate statements of the family members and witnesses.

But city police director Senior Superintendent Nelson Aganon said over the weekend that the Special Investigation Task Group (SITG) is still establishing the identities of the gunmen and mastermind, including the motive in the killing.

Rotoras, president of the University of Science and Technology of Southern Philippines, was shot dead outside his house last December 2.

READ: Gunmen 'used a ladder' in shooting Rotoras

Since then, police still have had no concrete and hard evidences that would lead to the identification of the gunmen and the mastermind.

Last week, Rotoras' brother Eldie announced publicly that the Rotoras siblings are submitting themselves to the probe.

Eldie also wanted Rotoras' widow, Zara Lynn, to be investigated following supposedly "odd behavior" of the widow as observed by the family.

READ: Rotoras widow now ‘person of interest’

However, Aganon said all allegations are welcome but it has to be verified and supported with hard evidence for it to stand in court.

"Anything is possible under the sun," Aganon said.

Aganon said they already secured the affidavits of the siblings and the widow.

He said investigators are treating all other personalities within Rotoras' circle before the assassination as persons of interest.

However, Aganon admitted that the SITG had a hard time looking for material evidences but he said investigators are exhausting all means to produce them.