This is a bizarre video. The police officers are trying to arrest a man who is mocking them and not cooperating. The officers decide to taser him rather than simply force his hands into cuffs. The man screams “I am being illegally tasered, I am defending myself” and proceeds to escape.
In defense of the officers, they repeatedly try to cuff him and do not taser him until he starts to swing his arms. However, the taser requires them to let go of the man which results in his escape. It is not clear why the two officers could not continue to hold the suspect and secure the cuffs without the use of the taser.