SAN DIEGO (CBS 8/ CNS) - On Friday, the firefighters who were wounded Wednesday during an on-duty stabbing assault spoke out about the incident.

San Diego firefighter Ben Vernon was released on Friday from Scripps Mercy Hospital. He thanked the medical staff, family and friends during a press conference.

Deputy District Attorney Steven Schott said 32-year-old Ben Vernon and 37-year-old Alex Wallbrett were among several firefighters who responded to a call of a sick man about 4 p.m. Wednesday at the trolley station in the 500 block of Park Boulevard.

Schott alleged that Jones refused orders to step away from the scene, then attacked transit officers before stabbing the two firefighters.

During the attack, Vernon suffered a punctured lung and Wallbrett was stabbed multiple times, but suffered lesser injuries.

A motive for the attack was unclear, but the man accused of stabbing two San Diego firefighters pleaded not guilty Friday to three charges, including attempted murder and assault with a deadly weapon.