The South Korean police said Thursday that a man, who had been signaling to other drivers to go around his car after it broke down in a tunnel, was run over and killed by another driver who was temporarily distracted and did not see him.

Officials are investigating a 20-something-year-old man for causing the accident at 4 a.m. on Wednesday, which fatally injured a man in his 40s, whose car had broken down. The younger man told investigators that he had been occupied with his smartphone's GPS navigation app when he hit the victim.

According to the officials, the victim’s car had broken down in the middle of Yondam Tunnel between Ansan and Hwaseong in southern Gyeonggi Province, a section of the Seohaean Expressway. After his car had abruptly stopped in the second lane of the three-lane expressway, he had exited the vehicle and started signaling to the other cars to drive around him.

But one of the drivers failed to see him and ran him over. The victim was carried to a nearby hospital via ambulance, but he eventually died.

The younger driver is being accused of violating the Act on Special Cases Concerning the Settlement of Traffic Accidents, specifically Article 3, which stipulates punishment for inflicting bodily injury due to gross negligence. It is punishable by up to five years in prison or a 20 million-won ($15,000) fine.