A Metro police officer died Thursday morning while trying to save a woman who was threatening to drive her car into the Cumberland River.

During the rescue attempt, 44-year-old Officer Eric Mumaw went missing in the river. His body was found hours later.

Mumaw, who was an 18-year veteran on the police force, is now being called a true hero. He leaves behind his longtime girlfriend and her daughter.

A criminal investigation is now underway while the driver, 40-year-old Juli Glisson, is questioned and detained by police. Police said she showed clear signs of intoxication and was being evaluated at a hospital.

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It all began around 4:20 a.m. Thursday when police received a 911 call from one of Glisson's relatives. They told police Glisson was at the boat ramp at Peeler Park and was having suicidal thoughts.

Mumaw and Officer Nick Diamond responded just minutes after receiving the call and found the car on the edge of the water.

The two officers talked with Glisson for about 10 minutes and tried to get her out of the car.

Metro Nashville Police Department spokesman Don Aaron said they believed Glisson was about to get out of the car when her driver's door opened, but the car suddenly rolled down the ramp and into the water around 4:35 a.m.

Aaron said the two officers made "heroic efforts" to save the woman. They both went into the freezing water, but the boat ramp ended abruptly, and they lost their balance.

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Mumaw slipped and was last seen about 50 or 60 yards into the river, which is is about 15 feet deep in that area, at 4:40 a.m.

Diamond was able to get back to the riverbank and saw his co-worker struggling.

"He was in despair in the water, and Officer Diamond was trying to grab him and actually had slight contact with him at some point, but could not maintain the grip," Aaron said.

A third officer, Officer Trent Craig, saw everything that happened and jumped into the river and tried to save Mumaw. Aaron said Craig was up to his neck in water and could not get to where Mumaw was.

Dozens of firefighters and police officers desperately searched the water for hours. Boats circled the water where he went under and a helicopter searched from the sky.

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At 8 a.m., about four hours later, a diver with the Nashville Fire Department found Mumaw's body about 70 yards from the boat ramp.

"Even though he lost his life, it's important that his body was recovered and he's now at peace," Aaron said.

Diamond was taken to Vanderbilt University Medical Center and was treated for hypothermia. He was released later in the morning.

Craig was treated at the scene for his injuries.

Glisson stayed inside the car as it submerged and was able to get out and swim to a riverbank. She was found by a fire department boat and was taken to TriStar Skyline Medical Center, where she remains in stable condition.

Aaron said they have detained Glisson and believe she may have been impaired by "some type of substance." She is now under investigation and could be facing criminal charges.

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[CLICK HERE to see slideshow of images from the scene of the water rescue.]

Mumaw had been with the police department for 18 years. He received the department's Lifesaving Award on April 27, 2011.

One of Mumaw's colleagues told Channel 4 that he loved working the midnight shift and always had a big smile on his face.

"Officer Mumaw died truly trying to save the life of someone else," Aaron said.

Aaron said police departments from all over the country have been reaching out and sharing their condolences.

Nashville Mayor Megan Barry released this statement:

Our worst fears were realized today when Officer Mumaw was recovered deceased from the Cumberland River after having given his life to save a woman in distress. Officer Mumaw dedicated his life to the safety and protection of us all, and today he gave his life to that calling. My thoughts and prayers are with Officer Mumaw’s family and friends and all of our Metro Nashville Police Officers today.

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I want to thank the men and women of our Metro Nashville Police Department and Nashville Fire Department, as well as the city of Hendersonville, Tennessee Highway Patrol, Tennessee Wildlife Resources Agency, and Army Corps of Engineers who all came together this morning to assist in the search for Officer Mumaw.

Barry said the Metro Courthouse, the Korean War Veterans Memorial Bridge and several other buildings will be lit up in blue on Thursday night in Mumaw's honor. Barry has also ordered for all Metro buildings to fly their flags at half-staff.

A memorial service is planned for Mumaw at Cornerstone Church in Madison on Monday at noon. Visitation will precede the service from 9 a.m. to noon.

An email address has been established for people to share their condolences with Mumaw's family.

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Stay with Channel 4 and WSMV.com for updates on this story.

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