Jason Brown (above) faces preliminary murder charges in the death of Lt Aaron Allan

The suspect in the fatal shooting of a police officer who was killed while responding to a car crash has been identified.

Jason Brown, a 28-year-old tattoo artist with a three-year-old son and no major criminal history, faces preliminary murder charges in the shooting of Lt Aaron Allan in Southport, Indiana on Thursday.

Witnesses say shots rang out from an overturned vehicle in a single car crash, as 38-year-old Allan attempted to help the occupants trapped inside.

The car is believed to have flipped over after striking the center median at a high rate of speed near Madison Avenue and Maynard Drive.

Close family friends of Brown have spoken out, expressing their shock that the normally 'timid' man would be implicated in such a horrific crime.

Scroll down for video

Allan (right) was responding to a single-car crash when shots rang out from inside the overturned car, where the occupants were still trapped inside, witnesses said

Allan (left) was a 20 year veteran of law enforcement with six years on the Southport force. Brown (right) faces charges in the police lieutenant's Thursday shooting death

The 38-year-old Allan was called to the traffic incident at around 2.30pm on Thursday

'He's shy, he's timid,' Traci Wagner, who has known Brown his whole life, told RTV6.

'He's just not - he's not - How would you say it? He's not the kind of person who goes out and creates trouble.'

'Jason lives for three things: tattoos, skateboarding and his son,' Wagner said.

Brown's social media accounts also show an apparent interest in handguns.

In one photo on Instagram, he poses with matching semi-auto pistols carrying extended magazines in each hand.

Another post on Facebook reads: 'Why do I carry a pistol? Because my AR15 doesn't fit in my pants,' referring to the popular semi-automatic rifle platform.

On July 24, three days before Allan was killed, Brown posted on Facebook that he was interested in bartering tattoo work for electronics, vehicles, or 'bang bangs'.

When someone replied publicly asking what a 'bang bang' was, Brown responded: 'A gun'.

Brown has no major criminal conviction history, with records showing four civil infractions and one misdemeanor, a 2013 bust for possession of marijuana or synthetic cannabinoid.

He was found guilty and spent 30 days in county jail for that charge.

Allan (center) had been called to the scene with a report of a car crash when shots rang out

A makeshift memorial is seen on Allan's police vehicle at Southport Police headquarters

'Something had to have happened. I don't know if the wreck triggered something in his mind. I don't know if they were being chased. I don't know. I don't know,' said Wagner.

Witnesses at the scene said shots flew from the overturned car while the occupants were still hanging upside down by their seat belts.

When an off-duty sheriff's deputy pulled over to assist, 'all you see is, like, a bullet go and look like it hit their car. It almost hit our car if we didn't back up,' Julian Dewbrew told WTHR.

All the while, other motorists were pulling over to help in what they thought was just a car crash scenario.

Allan, 38, is survived by his wife and children

'While the police were firing at the vehicle, they had to literally yell at people to get back,' Dewbrew said of the deputy and another officer from the Homecroft Police Department who responded in the minutes after Allan was shot.

Police returning fire struck one of the individuals in the overturned car, although it isn't clear if that was Brown or the other man in the car.

Both men are currently hospitalized, one with injuries from the crash, and the other with the gunshot wound.

The other occupant, who has not been named, has been interviewed as a witness and police say they are not pursing charges against him.

Brown faces preliminary charges of murder and marijuana possession.

Allan was a 20 year veteran of law enforcement, who had served the past six years on the Southport Police Department, in the enclave of Indianapolis.

He is survived by his wife and children.