@ Luc Lion
Your scenario seems to make some sense, otherwise it is difficult to picture. Although 2nd witness could have been in the opposite quadrant ( between noses). SBR1 was on a wider downwind, which would make sense because of speed differential. Cessna was departing circuit straight out from downwind ( or perhaps cleared for right turn out but turned early ). SBR1 turned base and had no visual on the Cessna - would the sun have been in the SBR1's eyes ?
Obviously no visual by either, although if the above is true, the Cessna would not have seen the SBR1. Where was the tower ? Where they in contact ?
The many times I have flown in and out of Brown Field, I was always wary of the mixed traffic, whether on prop ( private ) or jet ( Navy Dept).