Memory card found on the street labeled 'Homicide' leads to arrest of alleged killer

A man has been arrested for murder after a memory card labeled "Homicide at midtown Marriott" that contained videos and images of a violent attack was discovered on an Alaska street, authorities said.

A woman called Anchorage police on Sept. 30 to say she found an SD card lying on the ground, and that it contained disturbing videos from early September that showed a woman being beaten, raped and strangled, according to court documents.

The SD card contained 39 images and 12 videos, the court documents said.

Some of the footage showed a naked woman "moaning and struggling to breathe," and trying to fight back, documents said. In another video, the suspect is seen stomping on the woman's throat with his foot, documents said and laughing as he strangles her.

Images also showed the victim in the back of a truck, documents said. The victim was later identified as 30-year-old Kathleen Henry, police said Thursday.

Police have charged Brian Smith, 48, with first-degree murder, and said he had a room registered at that hotel in question during that time period and a car matching the truck seen on the footage, and that his accent matches the voice heard in the video, court documents said.

Detectives found that Smith's phone pinged "to a location on Rainbow Valley Road along the Seward Highway within minutes of the last still image from the SD card of the female in the back of the black truck," according to court documents.

On Oct. 2, two days after the SD card was found, Henry's remains were discovered near Seward Highway, the Anchorage Police Department said.

Smith was taken into custody at an Anchorage airport on Tuesday.

Smith has pleaded not guilty. His attorney declined to comment to ABC News on Friday.

A connection between the suspect and the victim was not clear.

The police department said it "extends its gratitude to the citizen who stepped forward with the evidence."

Her actions "played an instrumental role" and "serves as another example of when you see something suspicious, say something," said police.