Three members of a large Native American family living in the tiny town of Pryor, Montana, were shot, and two killed, while attempting to help what they thought was a motorist stranded on the Crow Reservation.

The three family members, Jason Shane, 51, Tana Shane, 47, and their daughter Jorah Shane, 26, stopped to help what they believed was a driver out of gas on a remote road on Wednesday. But when the three approached the driver’s green 1990 Ford Taurus, he pointed a gun at them, demanded money and shot at all three, killing Jason and Tana Shane.

Authorities charged 18-year-old Jesus Yeizon Deniz (also known as Jesus Yeizon Deniz Mendoza) with two counts of murder in federal court after Jorah Shane identified him from a photo. After he was apprehended in Wyoming, he told FBI agents that “he shot the victims because he was getting tired of waiting around, and because the daughter laughed at him”.

Jason, Tana and Jorah drove to remote Pryor Gap Road on the western edge of the Crow Reservation after Tana Shane said a driver appeared to be stranded.

Facebook Twitter Pinterest Family members embrace at the scene of a shooting in Pryor, Montana. Photograph: Casey Page/AP

Once the three arrived, however, and approached Deniz’s Ford sedan, Deniz pointed a .22-caliber rifle at them and told them to get out of the vehicle. Deniz demanded money, but they told him they had none. Deniz then marched the three away from their vehicle, apparently behind them.

Jorah’s mother told her daughter in a Native American language to run according to the Associated Press. Jorah told police she then heard a gunshot and turned around to see her father lying on the ground.

Jorah ran, heard her mother scream but didn’t turn around because she was too scared. She felt blood running down her face, a gunshot wound, and then felt a bullet strike her back.

She told agents that when she turned around she saw Deniz get into the family’s car and drive off.

Jorah began yelling for help, and someone from the nearby St Charles mission school drove to her. She told the driver she was hurt, and the driver walked to her parents, both lying face-down on the ground.

Terrified the shooter would return, Jorah got behind the wheel of the car that had responded to her calls for help and drove to her sister’s home, a short distance away, and she was taken to the hospital.

“Both my brother and sister-in-law have big hearts,” Jorah’s aunt Ada Shane told the AP, about why the couple went to help Deniz. “They’re always helping someone else.”

The Shanes leave behind five daughters and two sons, the Billings Gazette reported. The youngest of their children graduated from high school this year, the report said.

Deniz was later found in Meeteese, Wyoming, by a Park County sheriff’s deputy. Deniz is charged with two counts of murder in the US district court of Montana Billings. A hearing is scheduled for Friday, the AP reported.

The Associated Press contributed to this report.