Chicago police officer unintentionally shot by fellow officer

Police revealed a major update in the case of Krystal Rivera, the 36-year-old Chicago police officer killed Thursday night .

An initial police statement following the incident said an officer discharged a weapon during an encounter with an armed offender.

In a statement Friday, police said further investigation revealed that officer's weapon unintentionally struck Rivera.

Police said that officer's weapon was the only firearm discharged in the incident.

The statement also said an investigation into the circumstances leading to the initial investigative stop is ongoing.

The offender who pointed a rifle at officers is in custody, according to police, and an investigation into aggravated assault by that offender is also ongoing.

No further information was available.