Rodger, I think those who were there will add any correction, but Bf109's or Fw190's generally didn't have radar so were hunting by sight after being directed to the bomber streams by ground controllers, flak or searchlights. The use of single seater fighters was a bit of a desperate measure. The pilots were hand picked bomber pilots with excellent navigational skills so they had a better chance of finding "patrol areas" (fighter boxes) from where they could be directed by ground radar to the bomber stream. This method was more susceptible to jamming by window or special operatives in Lancs broadcasting fake directions in German or by simply swamping their frequencies.
Once the fighter boxes had been identified by the RAF, Mosquito nightfighters could then pick them off while they were loitering awaiting direction.
By reason of limited range (and no doubt the strain of searching for bombers) they would be limited to one sortie as by the time they had landed, refuelled and rearmed the bomber stream would have moved out of range.
That's why larger aircraft such as the Bf110 and Ju88 nightfighter variants were used. They could carry a larger crew able to operate airborne radar. 3 pairs of eyes had a better chance of locating bombers as well as being directed into the stream and then picking up targets on their own radar. They could stay with the bomber stream for considerably longer, too.
The 4 kills in one night would have been on the one sortie (Paul Szameitat if I recall correctly, who took charge of the Staffel in early Jan 44 only to be shot down and killed 14th Jan 44). It wasn't always just the bombers that got shot down!!
Whilst I understand regle's remark about the fighter being out of ammo, I just wonder why HIS gunners didn't fire!! After all, to be out of ammo, some other poor souls had not been so fortunate, nor would others on another night. But that's rewriting history, it happened and thanks to that he's still here with us! No doubt soaking up the sun in Hellfire Corner!!