I read in multiple sources that 30 people were killed in the bathroom. A large group that couldn’t make it outside took refuge there. When the police entered, Mateen retreated to the same bathroom. If what I read is correct, there were 31 hostages in there already. Mateen shot them all, and one survived.
That was an early report, and I haven’t seen exact confirmation. The below quote appears to corroborate it, however. At the time of the reference to “approximately 30 hostages,” the police were inside the club, and the only remaining hostages were in the bathroom.
‘Several explosives and an armoured vehicle were used to break through a wall of the nightclub and rescue approximately 30 hostages. The suspect was shot by a police officer during this intervention.’
https://www.theguardian.com/us-news/2016/jun/12/orlando-shooting-nightclub-pulse-gunman
Calling the people in the bathroom ‘hostages’ gives the police an excuse for not doing something sooner. I do not think they were hostages in the traditional sense, but rather Omar was in the process of killing them.