JACKSONVILLE, Fla. -- A Wendy's employee was killed Thursday afternoon after being shot by a co-worker, according to the Jacksonville Sheriff's Office.

Gunshots were fired at about 2:30 p.m. inside the Wendy's in the 3000 block of St. Johns Bluff Road on the Southside.

Police said they are searching for Thomas Theo Brown, whom they've identified as a suspect in the fatal shooting.

According to investigators, Brown was working at the fast-food restaurant when he got upset about something and left work.

"He went home and he said in a rage, 'I'm tired of this. I'm going to kill whomever,'" said JSO Sgt. Derrick Lewis.

Police said Brown returned to work with a gun and shot and killed fellow employee 22-year-old Juanese Miller.

There were several people inside the restaurant eating when the shooting happened.

"They're not letting us know anything right now. We're just waiting news," said Miller's niece, Annalisa Johnson.

Miller's family said the victim worked at the Wendy's for only a few months and that she was trying to earn a living so she could take care of her 3-year-old daughter.

A neighbor of Miller told Channel 4 that two days ago he gave Miller a ride to Wendy's because she had an ongoing feud with Brown and the two were having a sit-down meeting with their manager to discuss the problem.

Miller's family said it had not heard about any problems between Miller and Brown.

JSO said Brown is considered armed and dangerous. Officers said before Brown left the restaurant he announced that he was going to "make cops shoot him."

Brown is thought to have fled in a green four-door Honda Accord with Florida license plate number 391-JIV. Police said he was last seen wearing his Wendy's uniform.