Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
Charles Bronson is a Russian spy who goes to America to stop a guy from making telephone calls. Seriously, that's the plot. The guy is a disgruntled KGB agent who wants to start WWIII by activating people who were brainwashed in a top secret mind control program created in the 1950's during the height of the cold war. When he drops a dime in a phone booth and recites a Robert Frost poem they become mindless human time bombs who destroy American targets that were important 20 years ago but not so much now.
Near the end of the film, Bronson and Lee Remick go to a bar out in the sticks somewhere in Texas to try to stop one of the dial-a-terrorists. The bar has a couple of glass terrariums with rattlesnakes in them, including one named Gus with a sign saying he's "The largest diamond back rattler ever captured in the state of Texas" which is an exaggeration because he's not very big. Bronson needs a distraction so Remick knocks over the cages and the snakes get free. The distraction works - customers scream and two policemen start shooting at the snakes. The bartender woman screams "don't shoot Gus!" Then we watch poor Gus' head explode.
When you slow it down you can see that they used a limp dead snake and pulled its head up with a wire then shot it or set off a charge to blow it off.