A Pennsylvania man is accused of fatally punching another man while inside a Las Vegas casino hotel this summer, according to a police arrest report.

Michael Saunders, 42, of Pittsburgh was initially arrested on suspicion of battery after hitting someone inside The STRAT on Aug. 27. Court records indicate a murder charge has since been added.

In their arrest report, police say they were called to the hotel after someone was hit in the face and left unconscious. Security had detained the suspect, identified as Saunders, before he could leave the property.

The victim, identified as Thach Nguyen of Springfield, Virginia, was taken to a hospital, and police wrote he was diagnosed with a severe brain bleed and a skull fracture.

The Clark County Coroner's office confirmed that Nguyen, 73, died from blunt force head trauma, and his death was ruled a homicide.

Police said they reviewed the surveillance video and saw that Nguyen got into an argument with a woman while they were in line for check-in. Witnesses said the woman accused Nguyen of standing too close to her.

A man is captured on video approaching Nguyen from behind and punching him on the left side of his jaw, according to the arrest report. Nguyen fell to the ground and was unresponsive, and the man and woman tried to leave before they were detained.

Saunders initially told officers he believed Nguyen was trying to assault his fiancee and later told detectives during an interview that he could hear her say something to the effect of "Stop touching me" and "Get away from me."

"Saunders admitted that he didn't know what was going on and just saw a male close to [his fiancee] which caused him to punch him without regard or understanding of what the altercation was about," police wrote.

His next court appearance is scheduled for Oct. 19.