At some point in his life, Shane McKillen started to work as a mercenary, presumably working often and making himself noticed by Hamilton Dynamics. He began to be hired personally by its CEO Catherine Hamilton-Kane in order to do some dirty work for her.
Retrieving Alice's butterfly knife
After Kate Kane contacted Sophie Moore to give her Alice's butterfly knife she previously stole her to have it DNA tested and demonstrate the villainess was in fact her missing sister Beth, in order to cover the fact she faked the girl's death fifteen years prior, Catherine sent McKillen and a group of thugs led by him to attack Kate and Sophie out of the Crows Security headquarters dressed as member of Wonderland gang and retrieve it.
McKillen and his men are successful and he later had an encounter with Catherine in a park to give her the butterfly Kife, receiving from the woman the order to destroy it.
It's unclear if Shane McKillen also take some part in Alice's assassination attempt when the transfer truck she was being transported to Arkham Asylum was bombed by Hamilton Dynamics while on Loeb Bridge.
Infiltrating the Wonderland gang's hideout
After Alice blackmailed Catherine telling her to give her a top-secret weapon from her defense company until 10 pm the next night or Jacob Kane would have known all about how she convinced him that his daughter was dead all those years ago, in response Catherine sent a handful of men led by Shane McKillen into one of Alice's lairs; however the Wonderland gang easily capture them and, after having bound all of them to some chairs, the villainess started to do the counting in order to choose who would she had tortured first. Despite her counting the "winner" was another mercenary, eventually Alice's choice was to torture McKillen instead. A few hours later, McKillen met with Catherine in a parking garage showing her his severed pinkie, which was a message Alice intended to sent her. In anger, McKillen told Catherine that she would have to do it herself and left.
- Peak of human physical condition: As a mercenary directly under the Hamilton Dynamics' CEO, McKillen is likely in top physical condition, given the industry is one of the most important defense contractor company of the United States.
- Expert hand-to-hand combatant/Martial artist: McKillen is a highly skilled hand-to-hand combatant, he was able to hold his own against both the extremely skilled Kate Kane and Sophie Moore at the same time while posing as a member of the Wonderland gang.