A New Hampshire man accused of beating a 79-year-old victim to death in a Walmart parking lot has pleaded not guilty.

Brian Roberge, 52, of Somersworth, was being held without bail following his hearing. He faces a first-degree murder charge. 

Somersworth police said they received a call Friday about a man assaulting another man. When they arrived, they found Jan VanTassel, of Center Ossipee, unresponsive with head and facial injuries. 

He was pronounced dead at the scene. An autopsy concluded VanTassel’s cause of death was due to compressional asphyxia and that his manner of death was homicide, the New Hampshire's Attorney General's Office said.

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The Walmart logo on a store

A New Hampshire man allegedly beat a 79-year-old man to death in the parking lot of a Walmart last week. He has pleaded not guilty.  (ROBYN BECK/AFP via Getty Images)

"The compressional asphyxia finding by Dr. Weinberg is consistent with eyewitness accounts that Mr. Roberge was straddling Mr. VanTassel's chest for several minutes while hitting him in the head and face," the AG's office said. 

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Roberge appeared in court Monday via video. A judge ordered him to be held without bail, citing "convincing evidence" to detain him. 

Authorities have not revealed what led to the altercation between the two men. 

The Associated Press contributed to this report.