The Internal Affairs Division of a Virginia police department is investigating whether an officer improperly discharged a Taser, after stunning a suspect for more than 40 seconds when the man allegedly resisted arrest and tried to flee, police said.

Some of the incident was captured on video by a witness and posted to YouTube.

Several witnesses called 911 Saturday night to report that a gray Buick sedan had hit at least five parked cars on a street in downtown Fredricksburg, Va., police said. The driver of the car fled, but passenger Lantz Day, 36, remained on the scene and allegedly threatened bystanders, who called the police, Fredricksburg Police spokeswoman Natatia Bledsoe said.

A single officer arrived on the scene and "detained the suspect, but during the detention the subject refused to comply. He got up and fled from the officer," Bledsoe said. "That's where the video picks up."

On the video, shot on a cellphone at night, a man can be seen lying in the street. The distinctive sound of a stun gun being discharged can be heard for a little more than 40 seconds, as can the man's screaming.

Day was charged with obstruction of justice. He bonded out of jail for $3,500 Monday, and has not yet appeared in court or entered a plea. He could not be reached for comment today.

Police have not released the name of the officer.

Police said an investigation is routine in any incidence in which an officer uses force, and the pending inquest was not the result of Saturday's arrest being caught on video.

The investigation will focus only on the length of time the Taser was deployed, Bledsoe said, not that it was used at all.

"We're not investigating whether it should have been deployed. The suspect was legally detained, noncompliant and attempted to flee," she said.

An internal department memo, obtained by ABCNews.com, marked "Use of Force; Lethal and Less-Lethal Weapons," authorizes officers to use stun guns when trying to "arrest, detain, subdue, control, and/or restrain a non-compliant suspect," as well as to "prevent the escape of a suspect."

The memo, however, does not specify for how long a stun gun should be discharged.