It’s all about:
1) Luring the bad guy and a few of his most powerful minions away from the warehouse
2) Curb-stomping a few of the remaining minions and blowing up the rest
3) Kidnapping a scientist out of the zombie-making bunker below the (now burning) warehouse
4) Stuffing a jet ski* into the freight elevator and snapping the cable so it falls a long long way and blows up the zombie-making bunker and what’s left of the warehouse
5) Recruiting the kidnapped scientist into working for me in my genetics lab/incipient cult.
I mean, srsly. Exploding jet skis. Which I think Johnnie used as an improvised melee weapon during the curb-stomping phase.
*We all know from Waterworld that jet skis are the most explosive object known to man.