Deaths of innocent people; meaning of those aforementioned sentences

Students attacked in their classrooms while preparing for exams.

Gunmen believed isolated in the female dormitories.

Angela Merkel, Francois Hollande and Mariano Rajoy were briefed on the rescue and thanked the workers.

I really need someone to thoroughly explain the meaning of those aforementioned sentences.

When I saw the title I came to the conclusion that this must have been a terrible act on a campus. There are 3 sentences you used so I looked at the verbs that were used in each sentence and thought about the title. I understand these sentences to mean this:

Sentence 1: I don't know how these students were attacked. Yet, an attack can be physical or verbal. I would infer or guess that the attack was physical. However, you can only conclude this because of the title and the second sentence starts with "Gunmen".

Sentence 2: The subject is the gunmen, so if they were in a female dormitory and believed to be isolated, this means that these men were alone in an area of the dormitory.

Sentence 3: I'm unsure who these professionals are, but when there is a tragic event on a campus then law enforcement may give all of the necessary information to a campus representative and talk to reporters. In this case, they were told about a rescue. This could mean two things. Either there was a survivor or the rescue involved apprehending or capturing the gunmen.

I hope this helps! When I get confused about the meaning, I just look at the title and the verbs. Also, if this is a news article there maybe sentences at the beginning or the end of paragraphs that can give you more information about what really occurred.