The Congolese park rangers of the famous “gorilla selfies,” that became an instant internet sensation, have fallen victim to an attack that killed twelve park rangers and a driver following an ambush attack by Rwandan rebels.

According to the Daily Mail, the rangers were protecting the gorillas at the Virunga National Park, which is a UNESCO World Heritage Site in Northeastern Democratic Republic of Congo.

The April 24 attack was said to have been carried out by the Democratic Forces for the Liberation of Rwanda (FDLR), according to Congolese Major General Maurice Aguru Mamba, but the motives for the attack are yet to be confirmed.

In total, 18 people have been reported to have died in the attack. Reports indicate that 15 rangers had been escorting civilians when the ambush occurred; 12 rangers, the driver, and five civilians are among the dead.

The rangers at the park are armed and accompanied by sniffer dogs as the park is flanked by rebel militant groups. In the past twenty years, over 170 rangers have been murdered–making it a tremendously dangerous job.

Mathieu Shamavu, the ranger who was featured in the viral selfies, and had posted more selfies days before the attack, took to Twitter to write a message encouraging strength and unity following the ambush.

Lad Bible reported on a statement from Virunga National Park, which read:

“It is with great sadness that the Congolese Institute of the Conservation of Nature confirmed the identities of the Virunga Park Rangers and employees who tragically lost their lives after an attack on Friday. Our thoughts are with the families and friends of the victims, as well as with the animals whom they protected.