Attacker (noun)

1. A person or entity that makes a physical or verbal assault.
2. A person who carries out an attack, especially one who launches an armed assault.
3. A person or group who engages in hostile or aggressive behavior.

Origin:

From the verb 'attack' meaning to make an armed or hostile approach to.

Examples:

1. The attacker was caught by the police before he could escape.
2. The attackers were armed with guns and explosives.
3. The attacker was a member of a terrorist group.
4. The attacker was prosecuted for assault and battery.
5. The attacker was identified by the witnesses and arrested.