WARREN — When police first came upon 232 Mt. Horeb Road, one man was already lying in the driveway, shot dead. By the time authorities got a look inside, the same was true of that man's sister.

And by the time authorities entered the home, their killer — resident 48-year-old John Reno — was dead by his own hand. He was eventually found lying in a drainage ditch behind the home.

That's according to a harrowing account of a Sunday standoff with authorities released by the Somerset County Prosecutor's Office Monday afternoon. The account was also the first official acknowledgement of the names of those involved — including the two victims, Reno's 45-year-old live-in fiancé Heidi Errickson, and her brother, Frederick Errickson Jr.

Authorities believe Reno and Heidi Errickson got into an argument — and in response, he shot and killer her. Frederick Errickson Jr., 55, of Middlesex, went to the residence in an apparent effort to check on his sister’s welfare — and was shot as he approached the home, according to the prosecutor's office.

John Reno — whom MyCentralJersey.com reports had been arrested multiple times in Pennsylvania — may have a history of mental health issues, according to the prosecutor's office. It said authorities were working to confirm that.

According to the a joint statement by the prosecutor's office and Warren police, officers from the latter were dispatched to the home at 1:21 for a welfare check requested by a family member. Two minutes later, a pair of responding officers  saw the man later identified as Frederick Errickson Jr. dead in the driveway.

As the officers got out of their car, Reno fired an assault rifle at them, the prosecutor's office said. The cops radioed for backup and requested Somerset's SWAT team, but didn't return fire, the prosecutor's office said.

The SWAT team set up a permitter; crisis negotiators tried and failed to communicate with Reno. The prosecutor's office said a remote-controlled robot captured an image of Heidi Errickson laying dead in a first-floor Hallway.

When SWAT moved in and found Reno wasn't inside, they collapsed their permitter and found him dead in a drainage ditch in a densely wooded area behind the home, killed by a self-inflicted gunshot wound, the prosecutor's office said. Next to him was an a assault rifle with two high capacity magazines, it said.

The last gun shot—possibly that associated with Reno’s suicide—was heard at 1:33 p.m., the prosecutor's office said.

None of the first-responding officers who took Reno’s fire were physically hit or injured, the prosecutor's office said. But they were transported to a local hospital for stress-related symptoms and continue to receive appropriate treatment, it said.

In a recent Facebook post, Heidi Errickson called her fiance "amazing" and gushed about a wonderful life with him and her son.

MyCentralJersey.com also reports Heidi Errickson worked part-time for the Warren School District, which posted a notice to “address Sunday’s shooting incident.” The district is offering counseling on Monday and Tuesday for staff, parents and students with members of the Somerset County Traumatic Loss Coalition.

It said she was a widow, and lost her arm in an accident that also killed her then-husband.

My life is so complete I have a great kid that I absolutely adore. My fiancé John Reno is amazing. Who could of thought life could be this amazing again !!!! Dreams do come true it's all good !!

Posted by Heidi Lynn on Sunday, August 2, 2015

More From New Jersey 101.5 FM