In a tragic incident on Monday afternoon, a Canadian tourist lost their life and six others suffered injuries when a gunman took hostages atop a pyramid at Mexico’s Teotihuacan ruins.

The assailant ascended partway up the Pyramid of the Moon, a structure dating back nearly two millennia, known historically for human sacrifices. Around noon, the gunman began shooting at the terrified group before ultimately taking his own life, according to Mexican officials.

Among the casualties, four individuals were shot, while two others were hurt after leaping off the ancient monument. All the victims were women, comprising another Canadian, two Colombians, and a Russian national.

Footage circulating on social media depicts the masked gunman, armed with a pistol, walking back and forth on the platform as the hostages lay prone on the ground. In one clip shared by journalist Ricardo Ospina, the gunman is seen nonchalantly aiming and firing at a victim. Witness Laura Torres recounted to outlets including N+ Noticias, “I saw the shooter on the pyramid—there were many people, and he had hostages.”

Torres added, “Briefly, I saw him allow one girl to descend. I feared he might shoot her as she left, but thankfully he did not. Later, he released a boy, though the rest remained captive.”

The Pyramid of the Moon, constructed between 100 and 450 C.E., predates the Aztec civilization and was once part of Teotihuacan, one of the ancient world’s largest cities.

The structure lies on the north end of the Street of the Dead, opposite the larger Pyramid of the Sun, and was used for human and animal sacrifices, among other religious ceremonies.

Archeological evidence suggests most of these sacrifices were people captured from other parts of Mesoamerica.