A blackout in freediving

"He had started freediving 2 months before.He was an ex-swimmer and did scuba (so he was comfortable under the water and could equalise). There was nothing in his medical history to declare. Previous depths: 28 a few times. Didnt have fins and seemed keen to do unassisted a lot. I was going out to the 20m line, but he asked if we could go to the 30 instead. He said he wanted to try and break 28 meter.
I said fine. He had done a course with a local instructor and since he is focused on safety I did think that he was suitably responsible and aware of his own capabilities.

We swam out the 70 meter swim. He did one warm up that was not a long or good one and then he just went for depth instead of doing his second warm up. He didnt warn me or tell me anything - so I had to quickly get down to safety him. He did two "clean" dives - to 28 and then to 23. He had a fairly good style. I was doing passives - but safety-ing him in between - and asked him if he was allright - and wanted to do another dive.
He went down on his fourth dive, after about 35 seconds I went down and waited for him at 20 and could hear his contractions at about 15m. I was swimming right next to him with my hand on the back of his head ready to take him and he blacked out at 5 meters. I got him up and put his head back and on the buoy. Got his mask off and did the breathe-tap-talk breathe-tap-talk. And then he started gurgling and his eyes were rolling back - this lasted about a minute. Then he started to go purple in the face - and I knew that I couldnt get him back in to shore in time. He turned over (he was bigger than me and it was "choppy" in the water so was struggling to hold him up) and started to go down so I dragged him up and held his nose and gave him mouth to mouth (twice) I think that cleared his air ways and he started breathing again - but gurgling still. I got him back to the buoy and dragged his upper body over it and made him stay there. He started spitting a lot of blood in the first 2 spits - but the saliva came clear on the 3rd spit. He didnt spit water - but more saliva - if you know what I mean - it was more dense that pure water.

He didnt remember a thing - and said he was dreaming. He did dump his weight belt on the bottom though (he reached the bottom - so that makes it a 33m dive). A lot of the questions I was asking him about the dive - to find out how conscious he was of his body - of his dive - he couldnt answer me - he was not really "in" his body. He seemed more intent on depth than the quality of his dive.

We stayed on the buoy for a bit so that he could just recover - but then he wanted to dive again! Told him to forget it. We swam back in and I tried to get him to swim holding the buoy - but he sprinted off. I think that his ego was so heavily involved there - he couldnt face what almost happened. He did have enough energy to inform me that we were going to be going out to dinner together that night. He seemed to think that a date was the naturel progression from mouth to mouth recussitation - might have watched too many Baywatch episodes in his past!"