ESPN Senior NFL writer Jeremy Fowler discusses the investigation into Raiders LB Ray-Ray Armstrong's taunting of a police dog before Sunday's game against the Steelers. (2:20)

PITTSBURGH -- The Allegheny County Sheriff's Office is investigating a Raiders player, which a source with direct knowledge of the situation identified as linebacker Ray-Ray Armstrong, for allegedly taunting a K-9 service dog before Oakland's game Sunday against the Steelers.

The alleged crime would be considered a third-degree felony in Pennsylvania. Armstrong could face charges by the end of the week, according to the source.

The Raiders player barked at the dog, lifted his shirt and pounded his chest between exiting the locker room and entering the field area for warm-ups, according to Chief Deputy Kevin Kraus. Kraus said the player also told the deputy holding the K-9 to "send the dog."

"The dog was going crazy," Kraus said. "The deputy was trying to control the dog the best she could."

The sheriff's office notified the Steelers, the NFL and the Raiders of the investigation. It interviewed witnesses and obtained video surveillance, which captured a portion of the incident, but did not interview Armstrong before he left town.

Armstrong had no comment when approached by reporters Tuesday.

The Steelers consider this a police matter and did not comment. ESPN left messages with the Raiders and Armstrong's agent, Tony Paige, seeking comment. Armstrong could be subject to league discipline if arrested.

The Raiders signed Armstrong in October 2014 after the Rams cut him for committing an excessive number of penalties. He was a starter for Oakland and is now mostly a special teamer.

ESPN.com Raiders reporter Bill Williamson contributed to this report.