You've done this before, haven't you? Fine time for me to be out of bullets...
Mel is a wannabe mugger the Lone Wanderer may come across as a random encounter. He wants them to give him all their money. He will appear as friendly on the radar, and his clearly unassertive and stammering speaking voice make his demands indeed pathetic.
All right. I haven't killed anyone all day. Let's go.
I can't give you all my stuff, sorry.
If a skill-based topic is used, Mel will end the conversation without turning hostile, and will cower as if fleeing. If simply refused to be given anything, he may turn hostile. Mel will also fight any roving hostiles that travel near him (i.e. raiders or critters). But, since his shotgun is unloaded, he is limited to fighting unarmed. He is about as tough as an average raider, although without weapons, he makes a limited threat.
After speaking with the player character, Mel will hang around the area where they encountered him for the rest of the game. For a little while, he will be shown as 'fleeing', but afterwards hanging around the same spot forever.
Crouched in one spot, cowering with his arms protecting his head, Mel still counts as "fleeing" and cannot be pickpocketed.
Mel may run off to a gas station outside Old Olney and then say one of the following phrases...
Uh hey, I'm outta here, so see ya.
I mind my business, you mind your business.
I got nothing to say to you.
I'm not looking for trouble, or conversation either.
Even if Mel gets a weapon with ammunition from a nearby enemy, it is still possible to say it doesn't look loaded, and he will believe it.
Mel is an homage to Mel Gibson, the actor who played Mad Max. In Mad Max 2 Gibson threatened the Gyro Captain using an unloaded sawed-off shotgun. Ironically, the Gyro Captain believed him, whereas the Lone Wanderer does not believe Mel.