POMPANO BEACH, Fla. -

Nearly six years after a South Florida deputy was gunned down in a drugstore parking lot, authorities said Tuesday they have compelling evidence about a possible suspect.

Broward Sheriff's officials said Shawn Labeet may have been involved in the murder of Sgt. Christopher Reyka, who was shot to death in 2007, as he stepped from his cruiser to investigate a suspicious car outside a Pompano Beach Walgreens.

Authorities said they could not discuss most of the evidence gathered in the past 18 months, but did say Labeet was involved in drug rip-offs while he posed as a police officer. Authorities also said two witnesses placed Labeet at a business and an apartment complex near the drugstore the night Reyka was murdered.

Labeet was killed in a shootout with police in September 2007 after authorities said he shot four Miami-Dade police officers.

On the day of the shootout, police tried to pull Labeet over during a crime sting, but authorities said he kept driving, then went into his home, armed himself with an assault rifle and shot the police officers, fatally wounding Officer Jose Somohano. Miami-Dade police have said they don't have a clear motive behind Labeet's shootout with police that day.

They eventually tracked him to an apartment complex, where he was killed by the Miami-Dade SWAT team.

Reyka's death rocked the close-knit agency. Last fall, Reyka's son, Sean, joined the sheriff's office as a deputy. Sean Reyka, a former Marine, said he didn't join the sheriff's office to help avenge his father's death and said at the time that "justice will run its course."

Authorities said they've combed through thousands of tips and interviewed hundreds of people in their search for Reyka's killer. Now they're hoping someone from the public will come forward and fill in the missing details.

Authorities said in a news release that they want to know if anyone ever saw Labeet, who also lived in Miami-Dade under the alias of Kevin Wehner, with a firearm or driving a white vehicle. They're also trying to find out who his friends were and whether he was involved in any criminal activity before his death.

A $278,225 reward is being offered in the case. Tipsters can call the Reyka tip-line at (954) 880-3950.