Update 6 a.m. July 28, 2017: Police arrested Jason Brown, 28, on a preliminary murder charge in the shooting that killed Southport Police Lt. Aaron Allan.

Hendricks County court records show Brown was convicted of misdemeanor marijuana possession in 2014. A judge sentenced him to 30 days in jail.

Brown, who lives in Indianapolis, has three traffic tickets in Marion County and another in Greene County since 2009, online court records show.

What we know: The shooting of a Southport police officer

List:Officers killed in the line of duty

Photos:From the scene of Southport officer's killing

Brown remained hospitalized Friday in good condition, Indianapolis Metropolitan Police Sgt. Kendale Adams said.

Allan, 38, was responding to a traffic accident involving a car that had flipped over on Madison Avenue, a few blocks north of Southport Road.

As Allan approached, one of the occupants of the car started shooting. Whether the shooter was inside the car was unclear. A Homecroft Police officer and an off-duty Johnson County deputy had also stopped to help. They shot back, wounding the suspect, police said.

Johnson County Sheriff Doug Cox said the deputy involved is a reserve officer with his department.

The deputy was off duty, in civilian clothes, drove his personal vehicle and fired his personal handgun, Cox said.

The officer has a background in nursing. He saw the crash and stopped. He was trying to assist the victims before the suspect started shooting, Cox said.

Cox did not identify the deputy. The deputy will not be giving public statements, Cox said.

Update, 11 p.m., July 27, 2017:

The Indianapolis Fraternal Order of Police, Lodge No. 86, released this statement Thursday night upon learning of the tragic shooting and death of Lt. Aaron Allan.

“The Indianapolis Policing community is simply heartbroken by the tragic loss of Lieutenant Aaron Allan.

"Lt. Allan leaves a loving family, friends and his sisters and brothers of the Southport PD and the entire Indianapolis police community.

"Aaron made the ultimate sacrifice while actively trying to render help to his fellow man in need. There is no greater sacrifice and our entire community is now absorbing the impact of such a tragic event.”

The FOP offered its support to Allan's family and his "extended law enforcement family."

Earlier: A Southport police lieutenant was killed Thursday after walking up to a car that had flipped in a crash and one of the occupants shot him multiple times.

Lt. Aaron Allan, the Southport Police Department's officer of the year in 2015, was pronounced dead Thursday afternoon at Eskenazi Hospital, Southport Police Chief Thomas Vaughn said. He was 38.

"This afternoon we lost a brother,” Vaughn said.

Allan and an officer with the Homecroft Police Department were responding to a car crash involving a flipped vehicle shortly before 3 p.m. near the area of Madison Avenue and Maynard Drive on Indianapolis’ south side. As Allan approached the car, one of its two occupants opened fire. Whether the shooter was inside the car was unclear. Allan was hit multiple times, authorities said.

The Homecroft officer and an off-duty Johnson County Sheriff's deputy, who was in the area at the time, returned fire and struck the shooter, authorities said. Both occupants were taken to Eskenazi Hospital and were in police custody.

What prompted the shooter to fire at Allan was unclear. Officials with the Southport Police Department and the Indianapolis Metropolitan Police Department gave few details during a Thursday evening news conference.

“This will be handled just like one of our own officers,” IMPD Chief Bryan Roach said.

Tragedy:IMPD Deputy Chief Jim Waters dies after I-70 crash

After the shooting, dozens of police cars lined the streets of the neighborhood.

A mangled wrought-iron fence and the toppled black car were the only blemishes in the otherwise well-kept lawns that stretched down Madison Avenue.

As dark clouds rolled in, the red, white and blue police lights danced across the windows of a home where an American flag with a thin, blue line rustled in the breeze. Across the street, investigators sifted through ankle-high grass, leaving a trail of evidence markers in their wake.

For hours, neighbors gathered in clusters along the crime scene tape, swapping theories about what might have happened before the shots were fired. What they knew for certain: It was unlike anything they had seen in their quiet, close-knit community.

Tina Tom said she was shocked when a neighbor knocked on her door and said an officer had been shot in the street.

“It was alarming,” she said. "I had goosebumps all over my face and my whole body.”

Betty Strohm, who once lived in the home where the overturned car landed, said several police officers live in the immediate area.

“This is a great neighborhood,” Strohm said. “Everybody watches out for everybody here.”

She called the shooting “devastating.”

“This never should happen to any police officer, especially when they’re giving their time to help our community,” Strohm said, her voice straining. “This is very, very sad.”

At Eskenazi Hospital, officers and detectives were coming in and out. One person passing by told police, "Sorry about your comrade."

The Southport Police Department is a force of about 40 officers who are unpaid volunteers. The police chief is a paid position. Allan was working in a full-time paid position that began at the beginning of this year.

Allan had been with the department since 2011, according to a October 2015 article from the Southside Times.

He became the department’s first officer of the year in 2015 after being promoted to the head of Southport’s training division. When presenting the award to Allan, Vaughn highlighted a moment in August 2015 when Allan performed CPR on a man and saved his life.

Allan also had worked as a police officer for the Franklin Township Schools, a position he left in January, when he joined the Southport Police Department full-time, Chief Vaughn said.

Allen told the Southside Times that had he wanted to be a police officer since he was 5 years old.

At a news conference Thursday night, Vaughn remembered Allan as a dedicated public servant with a kind heart, fitting of his nickname: Teddy Bear.

"That’s because he tried to act real macho, but when a citizen or someone needed help, he was one of the first guys that was there," Vaughn said. "He didn’t always like that nickname, but it fit him."

Vaughn said the outpouring of support from community members and local and state police was encouraging.

"Without the support of our family, which is all police, it would be hard to get through this evening," he said.

Southport Mayor Russell McClure said at the news conference that he wasn't sure that Allan's loss had hit him yet.

"It comes as just a complete shock," McClure said. "It’s just a tragedy you just can’t imagine happening to your city, to one of your officers."

Call IndyStar reporter Justin L. Mack at (317) 444-6138 or email him at justin.mack@indystar.com. Follow him on Twitter: @justinlmack.

Call IndyStar reporter Holly Hays at (317) 444-6156. Follow her on Twitter: @hollyvhays.

Call IndyStar reporter Madeline Buckley at (317) 444-6083 or email her at madeline.buckley@indystar.com. Follow her on Twitter: @Mabuckley88.