Trump had at times privately talked about “fortifying a border wall with a water-filled trench, stocked with snakes or alligators, prompting aides to seek a cost estimate. He wanted the wall electrified, with spikes on top that could pierce human flesh.”

Additionally, after aides told him that his public suggestion of soldiers shooting migrants if they threw rocks was illegal, he backed down. But, he later suggested that they “shoot migrants in the legs to slow them down.”

“That’s not allowed either, (staff) told him,” according to the excerpt.

…The comments came around the same time [that Trump] publicly threatened to close the border, saying he would if “Mexico doesn’t get with it.” [He] later backed off from that threat. 

Border wall book details turbulent week of Donald Trump’s directives