Police in Mississippi are looking for a gunman who approached a uniformed officer outside a Biloxi police station and shot him dead overnight, just months before the veteran cop and married father-of-three was set to retire.

Authorities say the suspect walked up to on-duty Biloxi officer Robert McKeithen in the station's parking lot on Porter Avenue at 10.30pm on Sunday, shot him multiple times and then ran off.

Firefighters rushed McKeithen to the Merit Health emergency room down the street, where he was pronounced dead from his injuries about two hours later.

Smiling suspect: Police in Mississippi are searching for a man in a red beanie (left), who is suspected of walking up to on-duty police officer Robert McKeithen (right) overnight and shooting him multiple times, killing him

The shooting took place at 10.30pm outside the Biloxi police station on Porter Avenue

Biloxi police Chief John Miller said at a press conference on Monday that McKeithen had served on the force for 24 years and had plans to retire at the end of the year.

He is survived by his wife, two stepsons and a stepdaughter.

'He was a wonderful family man,' the chief said of the fallen officer. 'He was a very gentle man for a policeman, a likeable man who treated people with respect and dignity, and we’re going to miss him sorely.'

Miller called the gunman who took the officer's life an 'animal' and expressed a belief that he is still in the area.

Chief Leonard Papania, of the Gulfport Police Department, is leading the investigation, along with the Harrison County sheriff and prosecutors' offices.

Authorities released images showing the suspect with a wide grin on his face wearing navy blue shorts, a black T-shirt, a red beanie cap and dark high top sneakers with red caps.

The wanted man was described as having a thin build and standing between 5-foot-7 and 5-foot-10 tall.

Biloxi Police Chief John Miller is pictured laying a bouquet of flowers on Officer McKeithen's car in the police station's parking lot Monday

The wanted man was described as having a thin build and standing between 5-foot-7 and 5-foot-10 tall

Police are searching for the accused gunman on the ground and from the air Monday

A law enforcement helicopter has been flying over Biloxi as officers search the area.

Officials are pleading for the public’s help, saying there’s a $5,000 cash reward being offered through Crime Stoppers.

WLOX reported that Sunday's shooting marks the fifth time that the Biloxi Police Department lost an officer.