Both would seem OK in different contexts. To me, lucas21c going to save people this one suggests he must change his clothes before "going" to save people; probably he is at home, and wants to go elsewhere to save people, and before he "goes" to do that, he must change his clothes. lucas21c saving people This one sounds a little strange, but I wouldn't say it's incorrect.
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lucas21cgoing to save peoplethis one suggests he must change his clothes before "going" to save people; probably he is at home, and wants to go elsewhere to save people, and before he "goes" to do that, he must change his clothes.
lucas21csaving peopleThis one sounds a little