Mercer County man charged with first-degree murder in death of younger brother: DA

PRINCETON, N.J. - A New Jersey man has been charged with the murder of his younger brother after investigators say he called police to report the death after an apartment fire.

Matthew Hertgen, 31, is facing first-degree murder charges and other offenses in the death of his younger brother, 26-year-old Joseph Hertgen. 

Investigators say Matthew called police on Feb. 22 to report a fire and a dead body inside an apartment unit just outside of New Jersey's capital. 

Hertgen is also facing animal cruelty charged for the death of a cat and weapons offenses "related to possession of a knife and a golf club."

What we know:

Officers from the Princeton Police Department were called to the Michelle Mews Apartments on Saturday after Matthew Hertgen reported a fire and a dead body.

Investigators say Matthew's brother, 26-year-old Joseph Hertgen, was found dead with "injuries, including signs of blunt force trauma and lacerations."

The Mercer County Prosecutor's Office on Monday charged Matthew with first-degree murder and other charges, including animal cruelty for the death of a cat.

"The complaint alleges that Matthew purposefully or knowingly engaged in conduct that led to the death of his younger brother," prospecutor's said.

What we don't know:

The prosecutor's office said the cause and manner of Joseph's death are still pending the results of an autopsy.