Peace be upon you. It is generally advised to avoid killing animals unless they are harmful, in which case it may be permissible without causing suffering. However, there may be other prohibitions, such as if the animal belongs to someone or if it is against the law. According to Ayatollah Khamenei, caution should be exercised in such matters. Ayatollah Sistani states that it is permissible, especially if the animal is harmful. May you be successful in all good.