2003 Cavalier Stall - Scary experience

Today when I was driving my 2003 Cavalier (5 speed manual with 37k miles), after I changed gear from 5th to neutral to get ready to downshift to 4 th gear, suddenly both oil light and battery light went on, and I found that my steering wheel became very heavy to control. After I changed back to 5th gear, the lights went off, and things seemed to get back to normal. Since then I tried two or three times to downshift to another gear, everytime the lights went on and off and steering was hard to turn. Finally I was stopped by a red light, and found out that the engine lost power. I had to restart it, after which things seems to be all right.

It is kind of scary, because when the engine lost power I was exiting the highway, and I was scared to death to lose control of steering at that moment. Does anyone have any idea what might go wrong with this little thing? Thanks.