My brother passed away last night?

he was the closest person to me. I havent spoken to our mother in years.the guys that took him there said he collapsed in his job and then woke up but shortly after his chest started hurting. I called the hospital and they said when he arrived he was in full arrest? Thats all they could tell me what is that ? He did drugs and was a heavy alcohol drinker im in california hes in alabama he was only 23 thanks guys im confused what couldvd caused this and what is full arrest?