Izyum, Ukraine, is one of many towns that for months was controlled by Russian forces that relentlessly shelled the area and its people. The town was just recently liberated by Ukraine, and it was discovered that so many people were killed so quickly that hundreds were buried in shallow mass graves - including at least one entire family.

CBS News foreign correspondent Debora Patta visited the site on Friday, where she learned that the makeshift cemetery included those who were killed by shelling. Others buried had been executed, including some, according to Reuters, who were buried still with rope around their necks and their hands tied.

Dmytro Lubinets, the Ukrainian Parliament Commissioner for Human Rights, said in a video posted to Telegram on Friday that among those buried is "a whole family" - a mother and father in their 30s, their parents, and their 5- or 6-year-old daughter. The family's remains are marked with plywood crosses and small yellow and purple flowers planted in the dirt that covers them.

"We have testimony from locals stating they were all killed as a result of an air attack carried out by planes of the Russian Federation's military," Lubinets was translated as saying in Ukrainian.

Russian troops had control over the town for more than six months until Ukrainian forces were able to take it back earlier this week.

Izyum resident Serhii Shtanko told Reuters that he believes his neighbor's entire family, seven people in total, are also buried in the mass grave.

Patta reported that the bodies found at the site will be exhumed and identified in the days ahead.

Oleh Synehubov, the governor of the Kharkiv region, told Reuters that Ukrainian officials had received information about mass deaths while Russian forces still occupied the region, but it wasn't until now that they were able to confirm the casualties. Ukraine's head of national police Ihor Klymenko said early Friday that it's believed many of the bodies have been buried since March.

"Back then, we didn't have reliable information, but now, we have facts," he said. "There are many children, there are bodies with hands tied on their backs. Each of these facts will be investigated and they will get a legal review. Still, all of this can only testify that the world has to acknowledge that this is a genocide of the Ukrainian people."

Oleksandr Ilyenkov, Kharkiv's chief war crimes prosecutor, told Reuters it's believed there are about 500 civilian bodies at the site. These numbers would make it the biggest mass burial found in Europe since what was discovered in the aftermath of the Balkan wars, Reuters said.