Brian Wilson, and Jamie McGee

Nashville

Horrified onlookers watched as a motor home struck down a Metro Police officer only months out of the academy, the result of his attempt to aid in a minor accident that became a major tragedy.

Officer Michael Petrina, 25, was trying to direct traffic on Interstate 65 Saturday morning after a pickup overturned while taking the on-ramp from Old Hickory Boulevard. The motorhome's driver, Dean Joseph Diver, 71, of Key Largo, Fla., rounded a blind curve on the interstate, tried to navigate between Petrina's patrol car and a Tennessee Department of Transportation help truck — both parked on the interstate — and slammed into Petrina.

A witness looking down from the on-ramp, who was stuck in traffic from the first accident, said there was nothing Diver could do to avoid catastrophe. "He had the vehicle stopped 100 feet past the truck," Jeff Martin of Brentwood said. "He jumped right out within seconds and was urgently running back to see what had happened. The TDOT truck driver grabbed him and put his arm around him and walked him away from it."

But Petrina, who graduated the MNPD Academy in September, was already dead. Metro Police and the public will mourn him at noon Wednesday at First Baptist Church in downtown Nashville along with 43 city police officers killed in the line of duty. That annual memorial already was scheduled. Family funeral arrangements for Petrina are still pending.

In his short law-enforcement career, he'd already been recognized for his spirit and drive by his peers at the police academy, receiving the Christy Dedman Spirit Award for enthusiasm shown in training.

The award is named for the last Metro officer killed in the line of duty — struck by a tractor trailer while on Interstate 40 in 2004.

Petrina came to Nashville from the Memphis area after serving in the Tennessee Army National Guard and graduating from the University of Memphis with a criminal justice degree. The 25-year-old's job with the South Precinct was exactly the position he wanted, said his father, Jim Petrina of Germantown, Tenn.

"He loved life and he loved what he was doing," he said.

To his family, Jim Petrina said, the thought of his son's death was "the biggest fear we ever had." Michael Petrina also is survived by his mother, Joyce, and brother, Anthony.

Petrina's death deeply affected many officers who trained and eventually worked with him, Police Chief Steve Anderson said. Counseling will be available for South Precinct officers.

"(Officer Petrina) wanted to devote his life to public service, and he was well on his way to doing that," Anderson said at the scene.

No charges are being filed immediately in the case. Someone from the District Attorney General's office will look at the case file when the investigation is complete, police spokesman Don Aaron said.

Staff writer Heidi Hall contributed to this report. Reach Brian Wilson at 615-726-5970 or on Twitter @brianwilson17.