Who shot down Obst. Walter Oesau?

[Lagarto]

Hi everybody

Here's the story (I'm quoting from www.luftwaffe.cz): On 11 May 1944, Oesau, leading three aircraft of the Stabsschwarm, took off from Paderborn to intercept Allied bombers raiding north-eastern Belgium and Luxembourg. During his attack on the bombers he was bounced by escorting P-38s. In the ensuing combat he was shot down and killed in his Bf 109 G-6/AS (W.Nr. 20 601) “Green 13” near St Vith.

I know there was a vicious 20-minute-long dogfight at treetops, before Oesau fell.
The problem is I can't find a single comfirmed victory by a P-38 pilot on that day! Anyone knows any details? At least, which group was responsible for downing the famed Kommodore JG 1.