MIAMI -- A 21-year-old man in custody is considered the "prime suspect" in connection with the death of a Miami police detective who was found fatally shot inside a car in North Miami Beach early Tuesday morning.

Ricardo Ajuste, 21, was arrested early Wednesday morning but has not yet been charged with Detective James Walker's death, Miami police Lt. Bill Schwartz said Wednesday.

According to the Miami-Dade County corrections Web site, Ajuste was booked at the Pre-Trial Detention Center at 2:57 a.m. Schwartz initially said it was a tip that led police to Ajuste, but later said officers in the area picked him up sometime after the shooting.

Walker's body was found in an unmarked vehicle in an alleyway a block away from 1801 NE 164th St. The vehicle was riddled with bullets, Schwartz said.

Schwartz said although he was off-duty at the time of the shooting, "we believe that Detective Walker behaved as we expect our police officers to behave. He's a hero."

The shooting appeared to be brought on by a "jealous rage," according to Schwartz.

Schwartz said Ajuste's girlfriend had been out on a date with him earlier.

"After he left, she had another date with someone else," Schwartz said. "Ajuste returned with an AK-47 because he didn't take kindly to her having this other date."

Schwartz said Ajuste found her in a car with another guy and "shot the hell" out of the car, wounding the man in the arm. The man ran off, but Ajuste ran after him and continued to open fire, Schwartz said.

"We believe this is when Detective Walker, probably hearing these gunshots, drove into this mess," Schwartz said. "What exactly happened at this point is unclear. It's under investigation."

Walker was found slumped over the seat of the car with his gun in his hand, Schwartz said. The gun had been discharged.

Schwartz said Ajuste is a member of the One Way Gang.

"This area of North Miami Beach and this apartment complex, specifically, is a drug hole for the gang, and we heard that Ajuste is a major player in that gang," Schwartz said.

Police are checking to see if Ajuste's fingerprints are on the AK-47 found at the crime scene.

Currently, Ajuste is charged with two counts of attempted murder.

Walker, 30, was a detective with the Miami Police Department's domestic violence unit. He had been with the department since 2000.

Schwartz said police are still searching for a white Ford Taurus (2001 or later-model) with right rear-end damage and possible bullet holes. The vehicle was similar to the one in which Walker's body was found.

"When AK-47s are doing their thing, people can be nervous and think they see more than one car, but we're not sure yet," Schwartz said.

Detective's Widow Speaks About Husband's Fatal Shooting

Walker's widow spoke to Local 10 about her husband Wednesday, one day after he was shot and killed not far from the apartment where they lived.

"He's a quiet, reserved person -- very straight and narrow," Katinah Boursiquot said. "He doesn't do drugs. He doesn't even drink."

Walker had recently gotten back together with Boursiquot after a brief separation. The couple was together for 10 years and married for nine.

Boursiquot said she heard the shooting that ultimately took her husband's life.

"I heard three shots," she said. "At first, I thought they were fireworks, but they weren't. They were three gunshots."

As Ajuste faces charges in connection with Walker's death, Boursiquot said she forgives her husband's killer.

"I have no anger towards him because he was just in a state of rage and jealousy," she said. "I don't think he meant to harm my husband."