This paper addresses the leader-following $H_{\infty}$ consensus of linear multi-agent systems via distributed dynamic event-triggered control protocols. Both multi-agent systems with homogeneous and heterogeneous linear dynamics are considered. A novel dynamic event-triggering mechanism based on a unified time-and event-triggering framework is proposed. The open-loop estimation method is adopted to avoid continuous communication between neighboring agents. As a comparison, a static event-triggering mechanism is also studied in this work. It is shown that the $H_{\infty}$ consensus problem can be handled by the control protocols with the dynamic or static event-triggering mechanisms. At last, effectiveness of the proposed event-triggered control protocols are verified by two numerical examples, which shows that the dynamic event-triggering mechanism can further enlarge inter-event times.