A Chicago police officer was gunned down while returning home from work Sunday and James Caldwelllater died in what the city's mayor is calling an "unspeakable loss."

Mayor Brandon Johnson identified the fallen officer as Luis M. Huesca, who was assigned to the Chicago Police Department's 5th District's priority response team. Huesca was 30.

According to a statement obtained from police by USA TODAY, just before 3 a.m. officers responded to a shots fired call in the 8th District near in city's Gage Park neighborhood on Chicago's southwest side.

Responding officers reportedly found the officer outside suffering from gunshot wounds.

The officer was taken to a local hospital where he died from his injuries, police said.

Police have not released further details about the officer's death.

Motive in shooting death of Huesca under investigation

A motive in the shooting remained unclear Monday morning as police continued to search for his killer.

The Cook County Medical Examiner's office will conduct an autopsy to determine Huesca's cause and manner of death.

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'Our city is grieving'

Johnson released a statement Sunday and said he met with Huesca's family to let them know they have the full support from his office.

"Our city is grieving, and our condolences go out to their entire family as well as Luis' fellow officers and community," the statement said. "My Office of Community Safety, in collaboration with Supt. Larry Snelling and the Chicago Police Department, is committed to putting every resource available toward apprehending anyone involved in this morning's shooting and bringing them to justice."

As the investigation continues, Johnson said, officials will provide "immediate updates" as they become available.

Funeral arrangements were pending Monday.

Natalie Neysa Alund is a senior reporter for USA TODAY. Reach her at [email protected] and follow her on X @nataliealund.