Was George Justified of Killing Lennie

I think George was Justified of Killing Lennie Because If George let Lennie live he would Hurt more people and animals.Lennie doesn't know his own strength.In the story it said that "Lennie wanted to pet the puppy but instead he killed The pup.George Killed Lennie Because If Lennie ran off by his own He will Die and kill animals and Hurt Inocent People.