He openly admitted to massacreing peasants at lucanamarca:

In the face of reactionary military actions and the use of mesnadas (local defence squads against their SP ‘liberators’ – TF), we responded with a devastating action: Lucanamarca. Neither they nor we have forgotten it, to be sure, because they got an answer that they didn’t imagine possible. More than 80 were annihilated, that is the truth. And we say openly that there were excesses, as was analyzed in 1983. But everything in life has two aspects. Our task was to deal a devastating blow in order to put them in check, to make them understand that it was not going to be so easy. On some occasions, like that one, it was the Central Leadership itself that planned the action and gave instructions. That’s how it was. In that case, the principal thing is that we dealt them a devastating blow, and we checked them and they understood that they were dealing with a different kind of people’s fighters, that we weren’t the same as those they had fought before… If we were to give the masses a lot of restrictions, requirements and prohibitions, it would mean that deep down we didn’t want the waters to overflow. And what we needed was for the waters to overflow, to let the flood rage, because we know that when a river floods its banks it causes devastation, but then it returns to its riverbed. I repeat, this was explained clearly by Lenin, and this is how we understand those excesses. But, I insist, the main point was to make them understand that we were a hard nut to crack, and that we were ready for anything, anything”—Abimael Guzmán.

source https://socialistfight.com/2017/02/22/the-lucanamarca-massacre/

I posted more resources about Gonzalo above.