A 21-year-old man has been arrested for shooting and killing a San Francisco Bay Area police officer Wednesday, authorities said. He is being treated at a hospital for gunshot injuries.

Mark Estrada fired shots at Sgt. Scott Lunger at about 3:15 a.m. after being pulled over for rash driving, the Associated Press (AP) reported, citing Cpt. Mark Koller of Hayward police department. Lunger was reportedly rushed to Eden Medical Center in Castro Valley where he was pronounced dead.

"As Sgt. Lunger got out of the car and approached the driver side of the vehicle, the driver shot Sgt. Lunger without warning," Koller reportedly said. He added that another officer with the 48-year-old sergeant fired back at Estrada, who fled the scene in a white Chevrolet pickup. Authorities later found the vehicle abandoned in Oakland, Estrada’s hometown, CNN reported.

According to Hayward Police Chief Diane Urban, Estrada reportedly has connections with a gang but is not a “validated gang member.” It is not clear what charges would be pressed against him.

Alameda County Sheriff's Department, Hayward Police and the California Highway Patrol are jointly investigating the case, Police Lt. Eric Krimm said, according to the AP.

Lunger, who was a 15-year veteran in police force, is survived by his wife and two daughters. He was promoted to sergeant in 2009 and was also in the department's gang and SWAT teams. "He was an ideal police officer," Koller reportedly said.

This is the second such shooting in Bay Area on a police officer on duty. In March, San Jose police officer Michael Johnson was shot and killed while checking on 57-year-old Scott Dunham, who was reportedly suicidal and threatened to shoot himself and his wife. He fired several gunshots at Johnson who died on the scene. Dunham also suffered gunshot wounds and was found dead in his apartment the next day.