It is indeed passive but i understand that kill is an active verb, contrary to deceased or passed or died, where there is obfuscation of "by whom", which they did a lot since October (not just them)
The past participle of a verb is used as the passive participle (e.g. indicates the passive voice, where the patient of the verb is the subject and the agent is the indirect object). "She was killed" or "He was eaten" is in the passive voice, while "I died" or "I killed" is in the active voice. It's normally supposed to be preceded by an auxiliary verb (in this case "be"), but news titles omit the copula among other things.