Darrell Fuller, left, has been arrested for allegedly gunning down a carjacking victim and Nassau County Police Officer Arthur Lopez on Tuesday, Oct. 23, 2012.

The suspected gunman wanted for killing a 29-year-old Nassau County police officer and a carjacking victim near the Nassau-Queens border on Tuesday morning has been apprehended, authorities said.

Darrell Fuller, 33, was suffering from apparent self-inflicted gunshot wounds when he was arrested near the corner of 173th Street and 111th Avenue in Queens, police said. A police manhunt for Fuller had been underway since the slayings. He is hospitalized in guarded condition.

“It’s a complex investigation,” said Nassau Police Chief of Department Steven Skrynecki during a press briefing Tuesday evening. “There are hundreds of detectives working on this case right now.”

Charges and arraignment information were not immediately available.

It was the second time in six days a Nassau cop was killed in the line of duty. Officer Arthur Lopez, a member of the elite Emergency Services Unit, chased a hit-and-run driver until the Honda stopped at the corner of 241st Street and Jamaica Avenue in Bellerose Terrace, where the suspect shot Lopez in the chest, killing him at 11 a.m., police said.

“It was a very short exchange of words,” said  Skrynecki, noting the officer was not wearing a bullet-proof vest. Lopez’ partner, Officer Clarence Hudson, tried to help Lopez as the gunman fled in the Honda that was running on its rims, he said. Hudson is being treated for trauma.

The suspect then shot killed 52-year-old Raymond Facey of Jamaica, Queens during a carjacking on the Cross Island Parkway near Belmont Park Racetrack, fled in that victim’s vehicle, which he then abandoned in Queens, police said.

Fuller was previously convicted of attempted murder in Queens and selling crack-cocaine in Nassau County, according to authorities.

A witness told The Associated Press that the incident initially looked like a routine traffic stop.

“The officer’s walking up to the car. They just pulled out (a gun) and shot,” said Paul Walcott, a music producer from Bayside. “He went right down. He got hit point blank. He went straight down.”

“It’s a very sad day here in Nassau County as we just buried Police Officer Joseph Olivieri and we stand here today delivering terrible news,” County Executive Ed Mangano said, referring to the highway patrolman who was killed during an alleged drunken-driving crash probe Thursday on the Long Island Expressway. Olivieri’s funeral was Monday.

Lopez is the fourth Nassau cop killed since February 2011, when Highway Patrolman Michael Califano was fatally struck during a traffic stop on the LIE. Geoffrey Breitkopf, a plainclothes officer with the Bureau of Special Operations, was shot the following month by an MTA police officer during a friendly fire incident in Massapequa Park.

“To say that this is a difficult time would be an understatement,” said Nassau Police Benevolent Association President James Carver.

Nassau Police Commissioner Tom Dale said Lopez started as a patrol officer in the First Precinct eight years ago and was promoted to ESU in January 2010. He was also a volunteer firefighter with the Dix Hills Fire Department. He is survived by his sister, father and mother.

The Cross Island Parkway was closed in both directions at the Jamaica Avenue exit for several hours while investigators were on the scene. The northbound has since been opened but the southbound lane remained closed as of 7 p.m.