I spent a bit of time with my Silmarillion this morning to try and answer your question, but that only states that Ecthelion slew Gothmog who, in turn slew him. I don't have my copies of HOME at hand and that may give greater detail. I know I've read, however, that Ecthelion killed two balrogs with blade and edge, but was then assailed by Gothmog. His sword was broken and other weapons were of no use against this Balrog, and finally, bereft of weaponry, but still armed with his helm which featured a sharp point, he rushed his enemy, stabbing him with the point of his hel and driving him backward into the King's fountain wherein both contestants died.

If it wasn't Tolkien who wrote that, he probably should have - LOL. It makes for a great tale.

- Erulisse (one L)