Sean Suiter, an 18-year-veteran of Baltimore Police, died after being shot in the head with his own gun. This is what police are saying about the killing. (Claritza Jimenez/The Washington Post)

A Baltimore police detective was shot in the head with his own gun at close range while struggling with a man and died with his radio still clutched in his left hand, the city’s top law enforcement official said Wednesday.

Detective Sean Suiter’s death came a day before he was set to testify before a grand jury in an ongoing federal investigation of police corruption and drug shakedowns by an elite gun recovery unit.

Police Commissioner Kevin Davis said he was assured by prosecutors and the FBI that Suiter, an 18-year veteran of the force, was not a target of the investigation that has led to the indictments of eight current officers. Four have pleaded guilty to racketeering charges.

Davis said Suiter’s testimony was to have been about an incident several years ago involving some of the indicted officers. The commissioner sought to dispel notions Suiter was targeted the afternoon of Nov. 15 and said evidence gathered so far refutes the notion of a conspiracy.

“The encounter with a man was a spontaneous observation of a man behaving suspiciously and a spontaneous decision to investigate his conduct,” Davis said. But, he said, “I understand the speculation that exists.”

Members of the Baltimore Police Department gather near the scene of the shooting death of Detective Sean Suiter. (Patrick Semansky/AP)

Suiter and his partner were in the Harlem Park neighborhood canvassing about a December 2016 triple killing when they happened to twice notice a man acting suspiciously within a span of about 20 minutes, Davis said.

The department’s chief spokesman said Suiter, 43 and a married father of five, was not lured to Bennett Place, where he was shot, and that he had no appointment set there. Davis said Suiter confronted the man in an empty lot between two rowhouses but did not say what made him stand out.

The mystery surrounding Suiter’s death continues after a week with no arrests, no detailed description of the shooter and the fact that it appears only one gun was involved. A funeral for Suiter, who is originally from the District, is scheduled for Wednesday.

Davis said there was evidence found on Suiter’s shirt that indicated a struggle he called “brief and violent” and lasted mere seconds. Suiter made a radio transmission before he was killed that included what Davis said he believes are gunshots in the background. The commissioner said the words in that call have not been deciphered but that the recording is being analyzed with help from the FBI.

“He was clearly in distress,” Davis said of the sounds on Suiter’s radio call.

Authorities have previously stated that investigators found three shell casings that matched Suiter’s weapon, which was recovered at the scene. An autopsy Sunday ruled the death a homicide, Davis said, and also provided information about the trajectory of the bullet that caused police to return to the crime scene for another search. That repeat search recovered the bullet that killed Suiter, Davis said Wednesday.

Suiter’s partner, who has not been named publicly by the department and is considered a police witness in the shooting, Davis has said, took cover at the sound of gunfire and called in the shooting on his cellphone.

The partner has been continually talking with detectives, Davis said, and provided the spare description police said they have of the suspect as a black male wearing a black coat with a white stripe.

A reward for information leading to Suiter’s killer has reached $215,000, and Davis urged people to come forward.

In the days since the shooting, police have focused on Harlem Park, a small and violent patch of depressed real estate west of downtown in a city that ranks near the nation’s top in homicides per capita. Police kept the crime scene active for five days, restricting residents’ movements as they searched for the killer. The neighborhood is marked by more vacant houses than occupied homes.

“There is nothing we won’t consider,” Davis said. “Right now, the evidence that’s available to us is indicative of a homicide.” He said it would be entirely plausible for it to be coincidental that Suiter was killed in a random encounter unrelated to his pending grand jury appearance.

“It’s a very dangerous area,” Davis said. “He was following up on a brutal murder in 2016. Detective Suiter was not interviewing schoolteachers and mailmen.”

The commissioner said conspiracy theories swirling around the investigation are “certainly a distraction for leadership” and are “very hurtful for the Suiter family and friends.”

Suiter was a U.S. Navy veteran who had grown up in Washington and lived with his wife and family in Pennsylvania.

The commissioner said he met with homicide detectives Monday night on the investigation and that “they are determined to get it right.”