Who is to blame if a prankster literally gets knocked out by a martial artist?

Anonymous
A couple days ago my best friend's boyfriend wanted to stage a robbery prank on her. It backfired so miserably. He had no idea she knows Judo, Krav Maga and Brazilian Jiu Jitsu.

The prankster was the guy's friend pretending to be a mean robber that surprises and asks for her money. Neither of them were prepared for what would happen next. He got knocked out too fast that her boyfriend had to stop her boyfriend had to yell that it's just a prank. She's super pissed off at both. She claimed to have been so scared for her life that she really thought she was defending herself from harm.

She literally knocked out the prankster. Who is to blame?
Updates
+1 y
Her boyfriend is shocked. He didn't know he was dating a martial artist. He was so startled by her fast, moves and perfect aim. My friend is still pissed at both of them.
Who is to blame if a prankster literally gets knocked out by a martial artist?
7 Opinion