2000 Dodge Caravan Car won't crank;everything dead

My van was working fine. I parked it and went inside to work my 8 hour day. When I came out, it was dead. Nothing. I had a custodian come to give me a jump (figuring I may have not closed a door completely and the light wore the battery down. When he went to put the cables on, it sparked, smoked and melted my cables. I left it there and asked some people what it could be. They all told me the same thing--that the guy must not have put the cables on correctly. So someone else tried to jump it with cables on correctly and still sparked, smoked (we did use other cables, not the melted ones). He thinks it might be the starter. What do you think?