Elevated CPK from Excercise

I am a personal trainer. I have a client who started to train with me a month ago.

After a fitness assessment and a medical history, the client had cholesterol and no trygliceride, and from his family diabetic history he is predisposed to have diabetes, but not taking any medications . We started the first two weeks with a cardio exercise (not Exceeding 75% of the heart rate reserve), with body weight floor exercises.

After two weeks, I did the 1RM testing on the weight training machines.
The subject was feeling great training 6 days a week.

After one month, he was hyper and and sleeping only 3 hours a day.
I asked him to check with the physician. he did a blood test and his cpk level was high (around 5600).

Normally the first question was if he uses cocaine, but the answer was no.
His phsyician told him to stop exercising for 10 days, and asked for a calium/potassium test.

What do you think the problem is?  Would it be rhabdomyolisis?