question about pt109 incident

I recently saw a program on John Kennedy and pt109. Its not the first one i've seen, but it did raise what seems a rather obvious question that I had not thought of before and the program didn't seem to deal with. How exactly does a PT boat get run over by a destroyer?

Even in bad weather conditions, the size difference, manuverability difference and the noise an approaching destroyer would seem to make a head-on hit of a PT boat unlikely.

The only think I can think of would be if they were at a dead stop in the water with zero visibility or a panic turn in front of the destroyer was made.

Kennedy rightly deserves the highest praise for his actions after the collision, but was there ever an explaination (in detail) of how/why the collision happened? And were any other PT boats sunk in similar circumstances (collisions with large ships).

Kennedy's PT 109 was part of a group of PTs sent out on patrol on the night of Aug 1-2 1943 to look for and intercept the Japanese 'Tokyo Express' which was surreptitiously bringing troops and supplies to Japanese forces in the Solomon islands. Visibility was very poor. PT 109 was on its assigned patrol station, at idle speed on one engine, awaiting word of any contact with the enemy. A Japanese destroyer, travelling at an estimated 40 knots, appeared out of a mist at close range and rammed the PT, cutting it in two. The entire after action report can be found at:
http://www.history.navy.mil/faqs/faq60-11.htm

Walter S