That is deadly force. Blows to the head are prohibited if using something that can cause serious bodily harm. When I was training we couldn't use our flashlights, pr24 or anything like that to strike the head area!!!
Aaron Reichlin-Melnick"Tonk" is a Border Patrol slur that refers to the sound a metal flashlight makes when used to beat a migrant in the head. And that's the word that Border Patrol agents under the direct command of Greg Bovino were using when bragging about their arrests in Los Angeles last year.