A 16-year-old boy, shot once in the chest last night, was taken in serious condition to The Queen's Medical Center. His condition worsened this morning and he is now listed in critical condition, said Byran Cheplic, spokesman for Honolulu Emergency Services.

The search marks the third manhunt for a shooting suspect on O'ahu in a week.

The injured teen was shot at about 10:30 p.m., reportedly while sitting with friends in the library parking lot at 99-143 Moanalua Road.

Police said the gunman was reportedly a passenger in the backseat of a black car — possibly a recent Toyota model — with dark tinted windows. One shot was fired, said Honolulu Police Department detective Gary Lahens.

"Three young men were sitting in the library parking lot when a dark car came by and the shooter leaned out the backseat window and fired at the victim before they drove off," Lahens said.

He declined to comment on what may have prompted the shooting.

Hear more from detective Lahens in this video about the shooting.

The library fronts a strip mall that has a karaoke bar, several restaurants and other businesses. Juan Barquilla, an on-site security guard, said he was standing on the other side of the building when he heard a single shot.

"I came over and (the victim) was lying on the ground," Barquilla said. "I was scared. This was the first time I've experienced a shooting."

Barquilla said that earlier in the evening, at about 9:15 p.m., he had told the three juveniles to leave an area near a restaurant where they had apparently been drinking alcohol.

"They cooperated with no trouble," he said. "Two of them went over to the library parking lot and the third went to the gas station across the street. They were quiet."

Barquilla said after the shooting the victim's friends called 911. He said he did not hear any apparent arguing prior to the shooting. Also, he said he did not hear a car speeding away from the shooting scene.

The shooting was the third in seven days on O'ahu.

On May 14, Benjamin Grajeda, 27, of North Hollywood, Ca., was gunned down in Kane'ohe. Two suspects were arrested following a massive overnight manhunt on the North Shore. Police are continuing to look for a third suspect.

On Sunday, Dillon Ching, 30, died after being shot late Saturday during a brawl at Sunset Beach. No arrests have been made in the case.