A lone soldier from the United States, was killed on the Syrian border on Sunday morning when a hand grenade went off during a routine patrol. A Druze soldier was also killed in the blast, while three other soldiers were wounded in the incident, one of them seriously. Army officials are investigating whether the grenade was detonated accidentally or deliberately.

According to a senior IDF source, an IDF David light armored vehicle, carrying both soldiers and a commander from the 601 battalion, arrived at an army post near the town of Majdal Shams on Mount Hermon at approximately 7 A.M. after returning from a patrol in a military jeep. The soldiers, from the IDF’s Combat Engineering Brigade, were in the area to secure a border road.

The jeep reportedly came to stop about a meter away from the position’s concrete wall. “At this stage, a conversation began, and the driver exited the vehicle, holding the grenade,” the source said.

After exiting the vehicle, the driver walked towards the front, still holding the grenade. The lone soldier who was part of the checkpoint personnel, stood between the jeep and the wall. Suddenly, the hand grenade went off, killing both the lone soldier and the driver instantly.

“We do not understand the circumstances of this event yet,” the source continued. “The commander of the David vehicle then opened his door. That was when the blast occurred.”

An IDF Spokesperson’s Unit official identified the soldier who was guarding the post as Sergeant Shlomo Zalman Rindenow, 20, from New Jersey. Rindenow came to Israel on his own two years ago and did volunteer work raising and training rescue dogs in the community of Tapuah in Samaria. He later enlisted in the army, following in the footsteps of his five brothers, who served as combat soldiers.

Rindenow’s friends described him as a “handsome young man who always had a shy smile on his face, an erudite person who loved animals and people.” He is survived by his parents and eight siblings.

The jeep driver was identified as Staff Sgt. Hussam Tafesh, 24, a Druze reserve soldier from the village of Beit Jann. Tafish’s father told Army Radio that his son had replaced a friend as the driver, and was not supposed to take part in operational activity.

Tafesh is the grandson of Sheikh Abu-Mansour Hassan Tafesh, who served for many years as the caretaker of Nabi Shu’ayb, an important Druze and Muslim shrine near Tiberias. Tafesh’s family is widely known in Beit Jann, and the whole village mourned him on Sunday. He is survived by his parents and five siblings.

“This is a grave and difficult incident,” the source said.

Three other soldiers, including the patrol commander, were wounded in the incident. The patrol commander was evacuated by helicopter to Rambam Medical Center in Haifa, where he was listed in serious condition. The other two, who were lightly wounded by the shockwave, were taken there as well.

Army officials said that the soldiers’ families had been notified, and issued a statement expressing condolences to the soldiers’ families. “The IDF offers condolences to the bereaved families and will continue supporting them,” the statement said in part.

The reason for the incident is still unknown. Although it appeared to be an accident at first, the possibility of criminal motivation has arisen. OC Northern Command Maj. Gen. Aviv Kochavi has appointed a team of experts to investigate the incident.

“We have to understand why he exited the vehicle holding the grenade,” the source said. “This is something the committee of experts will determine.” While combat soldiers who take part in the clearing of border roads are armed with grenades, drivers of military vehicles are not.

Maj. Gen. Kochavi also ordered that all Northern Command soldiers immediately undergo a refresher course in grenade-handling protocol.

Tzvi Lev and Ariella Mendlowitz contributed to this article.