By Jon Herskovitz

(Reuters) - A man wanted for killing his former girlfriend fatally shot an Orlando, Florida, police officer on Monday, authorities said, prompting a manhunt and a reward of up to $60,000.

Helicopters buzzed the skies while scores of police shut streets and went door to door in their search for the suspect, identified as Markeith Loyd, 41. He was considered armed and dangerous.

An Orange County sheriff's deputy in the manhunt for Loyd was killed in a collision between his motorcycle and a van, police said. The driver of the van was a 78-year-old man, according to local TV station News 6.

"We are bringing this dirt bag to justice," Orlando Police Chief John Mina said of Loyd at a news conference, adding that federal agents had joined the search.

"We will track him down to the ends of the earth," he told a later news conference.

Authorities said the slain officer, Master Sergeant Debra Clayton, was shot while responding to a sighting of the suspect at a local Walmart. Loyd fired at her and she returned fire, Mina said, adding that he did not believe Loyd was hit.

Loyd fled the shooting scene outside the store in a car and fired at a deputy who tried to the stop him, authorities said. The deputy was unharmed.

Orlando Mayor Buddy Dyer declared a day of mourning after the officers' deaths.

Authorities have been trying to capture Loyd in connection with the December murder of a pregnant woman who was once his girlfriend, the Orange County Sheriff's office said.

Clayton, a decorated 17-year veteran of the Orlando Police Department, died at a hospital, the department said. Photos posted on social media showed her at community events, working to improve relations between police and residents.

"The Orlando Police Department family is heartbroken today," the department said on Twitter, showing a video of officers escorting a U.S. flag-draped gurney.

Local media said Clayton was one of the first officers to respond to the Pulse gay nightclub massacre in Orlando last June, the deadliest shooting rampage in modern U.S. history, where a gunman killed 49 people.

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Deputy First Class Norman Lewis, an 11-year-veteran, was killed in the manhunt for Loyd, the Orange County Sheriff's office said. Lewis, 35, once played football for the University of Central Florida. it said.

"Norm will be deeply missed. Rest in peace, gentle giant," it said on its Facebook page.





(Reporting by Jon Herskovitz; Editing by Dan Grebler and Andrew Hay)