strange problem with 02' dakota

When my dad left for work this morning the truck started fine, He stopped to get gas and when he opened the door to leave the dome light was flickering and a clicking sound like a relay of maybe something arcing could be heard. when he tried to start it it wouldn't turn over like the battery was dead. I came with jumper cables and it would crank but not fire up. It got towed to the dealer and they said the battery was no good and wouldn't hold a charge. They replaced the battery and all seems well. What the hell happened? Something caused this and I would assume something else was wrong that caused the battery to fry, not just a bad battery, and the real problem probaly still exists. Any ideas? I don't want it to happen again.

Batterys go bad all the time.They dont like heat and cold.My wifes car is an 04 Taurus and one try it started fine but 20 minutes later it wouldnt even try.