The Star reported that Allan responded to the scene of a crash around 2:30 p.m. Thursday in Homecroft, a small town just north of Southport.
Allan's department had previously named him "Officer of the Year" after saving two people in 2015.
Traci Wagner told RTV6 reporters that she had known Jason Brown his entire life.
In Indianapolis, on Thursday, a police officer went in to check for a vehicle crash which was reported to 911, and he was nearby thus dispatcher asked him to look for the incident, and it instead took his life, after he got shot multiple times near the crash site.
Brown had picked up a friend and was headed to a gas station when the auto picked up speed and crashed, court documents said. He says Brown was "hysterical" and Allan told Brown to be calm. Paramedics rushed Allan to the hospital, but document shows Allan "was pronounced dead at 3:25 pm Thursday".
Suspect Jason Brown is scheduled for an initial court hearing on Tuesday at 1:00 pm.
Brown remains in the hospital recovering from gunshot wounds sustained when officers reportedly returned the gunfire.More news: Sharapova to face Tsurenko at Stanford
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Bowman says Allan climbed into the vehicle, then Bowman turned to speak to a female witness when shots rang out. Brown was arrested on a preliminary charge of murder in connection with his death.
The gun used to kill Allan contained a magazine fit to hold 20 rounds.
Adams said investigators haven't said who was wounded and what prompted the shooting.
It is with unimaginable emotion, that the Allan Family would like to express our deepest gratitude, for the outpouring of support we have and continue to receive from the Community and across our Country.
Southport Police Chief Tom Vaughn says Allan always wanted to be a police officer, and he took his job to heart.
Allan was with the Southport Police Department for six years and had more than 20 years of law enforcement experience. He was 38 years old when he died, and he had also previously worked as an officer at the Indiana School for the Deaf, according to police officials.