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A gunman shot and killed a Florida police officer and injured three others Thursday, prompting a massive manhunt and a lockdown of several Miami-area schools, officials said.

Shawn Sherwin Labeet, 25, wearing a bullet-resistant vest, fired a high-powered weapon and fled the scene after officers approached his vehicle for a traffic stop, according to police.

Miami-Dade County Mayor Carlos Alvarez, a former police officer, said the "extremely violent" suspect "assassinated" a police officer.

"We need to find him as soon as possible and make sure that he's behind bars, where he belongs," Alvarez said.

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Police seized a car with a man, woman and two children in connection with the investigation, said Miami-Dade Police Department spokeswoman Linda O'Brien.

O'Brien said Labeet was last seen in neighboring Broward County in that car — a black four-door 2007 Pontiac Vibe with tag number W59-EPT.

Labeet was already wanted on an existing arrest warrant for aggravated assault in Broward County, O'Brien said.

A family friend of Labeet misled police and gave false information that helped Labeet get a step ahead of police looking for him, O'Brien said.

Police first reported Kevin Wehner as the suspect, but corrected that to Labeet as the investigation unfolded, saying Wehner was not involved in the incident.

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Helicopters, police officers and search teams combed the surrounding area for any signs of Labeet.

"Every moment that he is out there is too long," Robert Parker, spokesman for Miami-Dade Police Department, told FOX News.

The three injured officers are in serious condition, but are expected to survive, said a spokeswoman for the Miami-Dade Police Department.

Police described Labeet as a black male with a shaven face and short hair. Authorities said he left his Honda near a canal. Police found facial hair in his apartment, indicating he shaved his face.

The suspect purchased three high-powered weapons in March, police said.

The Honda will be examined for any type of evidence that could help find the suspect, said a spokeswoman for the Miami-Dade Police Department.

The officers were conducting burglary surveillance detail when they noticed a white Honda Accord being driven erratically at the entrance to a local neighborhood. When police stopped the vehicle, the driver shot the four officers and fled, authorities said.

"Truly this is a sad day for Miami-Dade County," Alvarez said at an afternoon news conference. "It’s gut-wrenching. It makes you sick to your stomach."

Police were urging residents to lock their doors and stay inside as police dog units and SWAT team members hunted the suspect.

Authorities had locked down Pines Villa Elementary, Mays Middle, Whigham Elementary and Centennial Middle schools. Children had the day off, but teachers were required to work.

Two of the victims were plainclothes officers and the other two were in uniform, Williams said.

The officers' identities were being withheld until their families were notified of the shootings.

The Associated Press contributed to this report.