男子购管制弩射杀流浪猫并发布虐猫视频博关注，已被拘留

为 + verb/noun phrase is used to show purpose or motive, similar to "in order to" or "for". In news language, it often introduces the reason behind an action.

并 is a formal connector often used in written Chinese, especially news reports, to link two related actions by the same subject. It means something like "and" or "furthermore".

已 means "already," and 被 marks the passive voice. The pattern 已被 + verb shows that someone or something has already undergone an action, often in formal or legal reporting.

对 + object + 实施 + action is a formal written pattern meaning to carry out an action against a target. It is common in legal, official, and news contexts.

后 means "afterwards" and 又 adds the sense of "again" or "then additionally." Together, 后又 is used to show a later action that follows the previous one, often adding another wrongdoing or event in sequence.